Engage NY Eureka Math 1st Grade Module 2 Lesson 25 Answer Key

A
*Write the missing number.

Question 1.
☐ = 4 + 1
5 = 4 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with one then we got five.

Question 2.
☐ = 4 + 2
6 = 4 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with two then we got six.

Question 3.
☐ = 4 + 3
7 = 4 + 3
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with three then we got seven.

Question 4.
☐ = 5 + 1
6 = 5 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with one then we got six.

Question 5.
☐ = 5 + 2
7 = 5 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with two then we got seven.

Question 6.
☐ = 5 + 3
8 = 5 + 3
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with three then we got eight.

Question 7.
☐ = 6 + 1
7 = 6 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add six with one then we got seven.

Question 8.
8 = 7 + ☐
8 = 7 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add seven with one then we got eight.

Question 9.
9 = 8 + ☐
9 = 8 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add eight with one then we got nine.

Question 10.
9 = ☐ + 1
9 = 8 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add eight with one then we got nine.

Question 11.
9 = ☐ + 9
9 = 0 + 9
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add zero with nine then we got nine.

Question 12.
8 = ☐ + 1
8 = 7 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add seven with one then we got eight.

Question 13.
☐ = 7 + 1
8 = 7 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add seven with one then we got eight.

Question 14.
10 = 8 + ☐
10 = 8 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add eight with two then we got ten.

Question 15.
10 = ☐ + 8
10 = 2 + 8
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add two with eight then we got ten.

Question 16.
7 + 3 = 4 + ☐
7 + 3 = 4 + 6

Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add seven with three then we got ten. ADD four with six then we got ten. Both expressions are equal.

Question 17.
6 + 4 = 5 + ☐
6 + 4 = 5 + 5
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add six with four then we got ten. ADD five with five then we got ten. Both expressions are equal.

Question 18.
5 + 5 = 6 + ☐
5 + 5 = 6 + 4
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add seven with three then we got ten. ADD four with six then we got ten. Both expressions are equal.

Question 19.
5 + 3 = ☐ + 1
5 + 3 = 7 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with three then we got eight. ADD seven with one then we got eight. Both expressions are equal.

Question 20.
5 + 4 = ☐ + 5
5 + 4 = 4 + 5
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with four then we got nine. ADD four with five then we got nine. Both expressions are equal.

Question 21.
4 + 5 = ☐ + 5
4 + 5 = 4 + 5
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with five then we got nine. ADD four with five then we got nine. Both expressions are equal.

Question 22.
2 + ☐ = 6 + 2
2 + 6 = 6 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add two with six then we got eight. ADD six with two then we got eight. Both expressions are equal.

Question 23.
4 + ☐ = 5 + 3
4 + 4 = 5 + 3
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with four then we got eight. ADD five with three then we got eight. Both expressions are equal.

Question 24.
☐ + 4 = 5 + 2
3 + 4 = 5 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with four then we got seven. ADD five with two then we got seven. Both expressions are equal.

Question 25.
☐ + 6 = 4 + 3
1 + 6 = 4 +3
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add one with six then we got seven. ADD four with three then we got seven. Both expressions are equal.

Question 26.
4 + 2 = 1 + ☐
4 + 2 = 1 + 5
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with two then we got six. ADD one with five then we got six. Both expressions are equal.

Question 27.
3 + 4 = ☐ + 2
3 + 4 = 5 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with four then we got seven. ADD five with two then we got seven. Both expressions are equal.

Question 28.
4 + 4 = 2 + ☐
4 + 4 = 2 + 6
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with four then we got eight. ADD two with six then we got eight. Both expressions are equal.

Question 29.
3 + ☐ = 2 + 7
3 + 6 = 2 + 7
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with six then we got nine. ADD two with seven then we got nine. Both expressions are equal.

Question 30.
☐ + 2 = 2 + 6
6 + 2 = 2 + 6
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add six with two then we got eight. ADD two with six then we got eight. Both expressions are equal.

B
*Write the missing number.

Question 1.
☐ = 3 + 1
4 = 3 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with one then we got four.

Question 2.
☐ = 3 + 2
5 = 3 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with two then we got five.

Question 3.
☐ = 3 + 3
6 = 3 + 3
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with three then we got six.

Question 4.
☐ = 4 + 1
5 = 4 + 1

Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with one then we got five.

Question 5.
☐ = 4 + 2
6 = 4 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with two then we got six.

Question 6.
☐ = 4 + 3
7 = 4 + 3
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with three then we got seven.

Question 7.
☐ = 5 + 1
6 = 5 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with one then we got six.

Question 8.
8 = 1 + ☐
8 = 1 + 7
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add one with seven then we got eight.

Question 9.
9 = 1 + ☐
9 = 1 + 8
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add one with eight then we got nine.

Question 10.
8 = ☐ + 7
8 = 1 + 7
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add one with seven then we got eight.

Question 11.
8 = ☐ + 8
8 = 0 + 8
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add zero with eight then we got eight.

Question 12.
7 = ☐ + 1
7 = 6 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add six with one then we got seven.

Question 13.
☐ = 6 + 1
7 = 6 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add six with one then we got seven.

Question 14.
10 = 9 + ☐
10 = 9 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add nine with one then we got ten.

Question 15.
10 = ☐ + 9
10 = 1 + 9
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add one with nine then we got ten.

Question 16.
5 + 5 = 4 + ☐
5 + 5 = 4 + 6
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with five then we got ten. ADD four with six then we got ten. Both expressions are equal.

Question 17.
6 + 4 = 7 + ☐
6 + 4 = 7 + 3
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add six with four then we got ten. ADD seven with three then we got ten. Both expressions are equal.

Question 18.
3 + 7 = 8 + ☐
3 + 7 = 8 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with seven then we got ten. ADD eight with two then we got ten. Both expressions are equal.

Question 19.
5 + 2 = ☐ + 1
5 + 2 = 6 + 1
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with two then we got seven. ADD six with one then we got seven. Both expressions are equal.

Question 20.
5 + 3 = ☐ + 5
5 + 3 = 3 + 5
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add five with three then we got eight. ADD three with five then we got eight. Both expressions are equal.

Question 21.
4 + 4 = ☐ + 4
4 + 4 = 4 + 4
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with four then we got eight. ADD four with four then we got eight. Both expressions are equal.

Question 22.
3 + ☐ = 6 + 3
3 + 6 = 6 + 3
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with six then we got nine. ADD six with three then we got nine. Both expressions are equal.

Question 23.
4 + ☐ = 5 + 4
4 + 5 = 5 + 4
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with five then we got nine. ADD five with four then we got nine. Both expressions are equal.

Question 24.
☐ + 4 = 2 + 5
3 + 4 = 2 + 5
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with four then we got seven. ADD two with five then we got seven. Both expressions are equal.

Question 25.
☐ + 6 = 3 + 4
1 + 6 = 3 + 4
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add one with six then we got seven. ADD three with four then we got seven. Both expressions are equal.

Question 26.
4 + 3 = 1 + ☐
4 + 3 = 1 + 6
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with three then we got seven. ADD one with six then we got seven. Both expressions are equal.

Question 27.
4 + 4 = ☐ + 2
4 + 4 = 6 + 2
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with four then we got eight. ADD six with two then we got eight. Both expressions are equal.

Question 28.
4 + 5 = 2 + ☐
4 + 5 = 2 + 7
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add four with five then we got nine. ADD two with seven then we got nine. Both expressions are equal.

Question 29.
3 + ☐ = 2 + 6
3 + 5 = 2 + 6
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add three with five then we got eight. ADD two with six then we got eight. Both expressions are equal.

Question 30.
☐ + 2 = 2 + 7
7 + 2 = 2 + 7
Explanation:
An addition sentence is a mathematical expression that shows two or more values added together. Add seven with two then we got nine. ADD two with seven then we got nine. Both expressions are equal.

Eureka Math Grade 1 Module 2 Lesson 25 Problem Set Answer Key

Use the expression cards to play Memory. Write the matching expressions to make true number sentences.

Question 1.

17- 5 = 12
10 + 2 = 12
Explanation:
In the above image we can observe a expressions 17 – 5 and 10 + 2. A number bond is a simple addition of two numbers that add up to give the sum. Make seventeen into two parts as ten and seven. Subtract five from ten then we got five. ADD five with seven then we got twelve. By adding ten and two results twelve. Both expressions are equal.

Question 2.

4 + 8 = 12
9 + 3= 12
Explanation:
In the above image we can observe a expression 4 + 8 and 9 +3. A number bond is a simple addition of two numbers that add up to give the sum. Make three into two parts as two and one. ADD nine with one then we got ten. ADD ten with two then we got twelve. Make four into two parts two and two. ADD two with eight then we got ten. By adding ten and two results twelve. Both expressions are equal.

Question 3.

15 – 8 = 7
16 – 9 = 7
Explanation:
In the above image we can observe a expression 15 – 8 and 16 – 9. A number bond is a simple addition of two numbers that add up to give the sum. Make fifteen into two parts as ten and five. Subtract eight from ten then we got two. ADD two with five then we got seven. Make sixteen into two parts ten and six. Subtract nine from ten then we got one. ADD one with six then we got seven. Both expressions are equal.

Question 4.

13 – 6 = 7
11 – 4 = 7
Explanation:
In the above image we can observe a expression 13 – 6 and 11 – 4. A number bond is a simple addition of two numbers that add up to give the sum. Make thirteen into two parts as ten and three. Subtract six from ten then we got four. ADD four with three then we got seven. Make eleven into two parts ten and one. Subtract four from ten then we got six. ADD one with six then we got seven. Both expressions are equal.

Question 5.

12 + 4 = 16
14 + 2 = 16
Explanation:
In the above image we can observe a expression 12 + 4 and 14 + 2. A number bond is a simple addition of two numbers that add up to give the sum. ADD twelve with four then we got sixteen. By adding fourteen and two results sixteen. Both expressions are equal.

Question 6.
Write a true number sentence using the expressions that you have left over. Use pictures and words to show how you know two of the expressions have the same unknown numbers.

Both sides equal to 16.
Explanation:
In the above image we can observe a expression 9 + 7 and 10 + 6. A number bond is a simple addition of two numbers that add up to give the sum. Make seven into two parts as one and six. ADD ten with six then we got sixteen. Both expressions are equal.

Question 7.
Use other facts you know to write at least two true number sentences similar to the type above.
9 + 2 = 10 + 1
4 + 5 = 8 + 1
Explanation:
In the above image we can observe a two number sentences 9 + 2 = 10 + 1 and 4 + 5 = 8 + 1. In 9 + 2 = 10 + 1 number sentence break two into two parts as one and one. ADD nine with one then we got ten. ADD ten with one then we got eleven. Both expressions are equal in this number sentence. In 4 + 5 = 8 + 1 number sentence ADD four with five then we got nine. By adding eight with one then we got nine. Both expressions are equal in this number sentence.

Question 8.
The following addition number sentences are FALSE. Change one number in each problem to make a TRUE number sentence, and rewrite the number sentence.
a. 8 + 5 = 10 + 2 _______

8 + 4 = 12
10 + 2 = 12
The number sentence is 8 + 4 = 10 + 2.
Explanation:
In the above image we can observe a number sentence 8 + 5 = 10 = 2. This number sentence is false. So we have to change one number to make a true number sentence. So cross out five and change it to four. In 8 + 4 expression break four into two parts as two and two. ADD two with eight then we got ten. ADD ten with two then we got twelve. By adding ten and two expression results twelve. Now both number sentences are equal.

b. 9 + 3 = 8 + 5 = _______

10 + 3 = 13
8 + 5 = 13
The number sentence is 10 + 3 = 8 + 5.
Explanation:
In the above image we can observe a number sentence 9 + 3 = 8 + 5. This number sentence is false. So we have to change one number to make a true number sentence. So cross out nine and change it to ten. In 8 + 5 expression break five into two parts as two and three. ADD eight with two then we got ten. ADD three with ten then we got thirteen. By adding ten and three expression results thirteen. Now both number sentences are equal.

c. 10 + 3 = 7 + 5 = _______

10 + 2 = 12
7 + 5 = 12
The number sentence is 10 + 2 = 7 + 5.
Explanation:
In the above image we can observe a number sentence 10 + 3 = 7 + 5. This number sentence is false. So we have to change one number to make a true number sentence. So cross out three and change it to two. In 7 + 5 expression break five into two parts as two and three. ADD seven with three then we got ten. ADD two with ten then we got twelve. By adding ten and two expression results twelve. Now both number sentences are equal.

Question 9.
The following subtraction number sentences are FALSE. Change one number in each problem to make a TRUE number sentence, and rewrite the number sentence.
a. 12 – 8 = 1 + 2 = ________

12 – 8 = 4
2 + 2 = 4
The number sentence is 12 – 8 = 2 + 2.
Explanation:
In the above image we can observe a number sentence 12 – 8 = 1 + 2. This number sentence is false. So we have to change one number to make a true number sentence. In 12 – 8 expression break twelve into two parts as ten and two. Subtract eight from ten then we got two. ADD two with two then we got four. In 1 + 2 expression Change one into two to make a true number sentence. ADD two with two then we got four. Both expressions are equal.

b. 13 – 9 = 1 + 4 = ________

14 – 9 = 5
1 + 4 = 5
The number sentence is 14 – 9 = 1 + 4.
Explanation:
In the above image we can observe a number sentence 13 – 9 = 1 + 4. This number sentence is false. So we have to change one number to make a true number sentence. So cross out thirteen and change it to fourteen. In 14 – 9 expression break fourteen into two parts as ten and four. Subtract nine from ten then we got one. ADD four with one then we got five. ADD one with four then we got five. Now both number sentences are equal.

c. 1 + 3 = 14 – 9 = ________

1 + 3 = 4
14 – 10 = 4
The number sentence is 1 + 3 = 14 – 10.
Explanation:
In the above image we can observe a number sentence 1 + 3 = 14 – 10. This number sentence is false. So we have to change one number to make a true number sentence. So cross out nine and change it to ten. In 14 – 10 expression break fourteen into two parts as ten and four. Subtract ten from ten then we got zero. ADD four with zero then we got four. ADD one with three then we got four. Now both number sentences are equal.

Eureka Math Grade 1 Module 2 Lesson 25 Exit Ticket Answer Key

You are given these new expression cards. Write matching expressions to make true number sentences.

Explanation:
1. In the above image we can observe a expression 3 + 2 and 12 – 7. A number bond is a simple addition of two numbers that add up to give the sum. In 12 – 7 expression break twelve into two parts as ten and two. Subtract seven from ten then we got three. ADD three with two  then we got five. By adding three and two expression results five Both expressions are equal.
2. In the above image we can observe a expression 8 + 9 and 19 – 2. A number bond is a simple addition of two numbers that add up to give the sum. In 19 – 2 expression break nineteen into two parts as ten and nine. Subtract two from ten then we got eight. ADD eight with nine then we got seventeen. In 8 + 9 expression break eight into two parts as one and seven. ADD one with nine then we got ten. By adding ten and seven results seventeen. Both expressions are equal.
3. In the above image we can observe a expression 1 + 4 and 14 – 9. A number bond is a simple addition of two numbers that add up to give the sum. In 14 – 9 expression break fourteen into two parts as ten and four. Subtract nine from ten then we got one. ADD one with four then we got five. By adding one and four expression results five Both expressions are equal.
4. In the above image we can observe a expression 10 + 7 and 2 + 15. A number bond is a simple addition of two numbers that add up to give the sum. Break fifteen into two parts as ten and five. ADD five with two then we got seven. ADD ten with seven then we got seventeen. By adding ten and seven expression results seventeen. Both expressions are equal.

Question 1.
Circle “true” or “false.”

 Equation True or False? a. 2 + 3 = 5 + 1 True  /  False b. 7 + 9 = 6 + 10 True  /  False c. 11 – 8 = 12 – 9 True  /  False d. 15 – 4 = 14 – 5 True  /  False e. 18 – 6 = 2 + 10 True  /  False f. 15 – 8 = 2 + 5 True  /  False

Explanation:
a. In the above image we can observe 2 + 3 = 5 + 1 number sentence. By adding two with three results five. By adding five with one results six. Both expressions are not equal. So the number sentence is not correct. Draw a circle for False.
b. In the above image we can observe 7 + 9 = 6 + 10 number sentence. In 7 + 9 expression break seven into two parts as one and six. ADD one with nine then we got ten. ADD ten with six then we got sixteen. By adding six and ten expression results sixteen. Both expressions are equal. So the number sentence is correct. Draw a circle for True.
c. In the above image we can observe 11 – 8 = 12 – 9 number sentence. In 11 – 8 expression break eleven into two parts as one and ten. Subtract eight from ten then we got two. ADD two with one then we got three. In 12 – 9 expression break twelve into two parts as ten and two. Subtract nine from ten then we got one. ADD one with two then we got three. Both expressions are equal. So the number sentence is correct. Draw a circle for True.
d. In the above image we can observe 15 – 4 = 14 – 5 number sentence. In 15 – 4 expression break fifteen into two parts as five and ten. Subtract four from ten then we got six. ADD six with five then we got eleven. In 14 – 5 expression break fourteen into two parts as ten and four. Subtract five from ten then we got five. ADD five with five then we got ten. Both expressions are  not equal. So the number sentence is not correct. Draw a circle for False.
e. In the above image we can observe 18 – 6 = 2 + 10 number sentence. In 18 – 6 expression break eighteen into two parts as ten and eight. Subtract six from ten then we got four. ADD four with eight then we got twelve. By adding two and ten expression results twelve. Both expressions are equal. So the number sentence is correct. Draw a circle for True.
f. In the above image we can observe 15 – 8 = 2 + 5  number sentence. In 15 – 8 expression break fifteen into two parts as ten and five. Subtract eight from ten then we got two. ADD two with five then we got seven. By adding two and five expression results seven. Both expressions are equal. So the number sentence is correct. Draw a circle for True.

Question 2.
Lola and Charlie are using expression cards to make true number sentences. Use pictures and words to show who is right.

a. Lola picked 4 + 8, and Charlie picked 9 + 3. Lola says these expressions are equal, but Charlie disagrees. Who is right? Explain your thinking.

Both expressions are equal. So Lola is right.
Explanation:
In the above image we can observe two expressions 4 + 8 and 9 + 3.In that expressions Lola picked 4 + 8 and Charlie picked 9 + 3. Lola says these expressions are equal, but Charlie disagrees. In 8 + 4 expression break four into two parts as two and two. ADD two with eight then we got ten. ADD ten with two results twelve. In 9 + 3 expression break three into two parts as one and two. ADD one with nine then we got ten. ADD ten with two results twelve. Both expressions are equal. So Lola is right.

b. Charlie picked 11 – 4, and Lola picked 6 + 1. Charlie says these expressions are not equal, but Lola disagrees. Who is right? Use a picture to explain your thinking.

Both expressions are equal. So Lola is right.
Explanation:
In the above image we can observe two expressions 11 – 4 and 6 + 1. In that expressions Charlie picked 11 – 4 and Lola picked        6 + 1. Charlie says these expressions are not equal, but Lola disagrees. In 11 – 4 expression break eleven into two parts as ten and one. Subtract four from ten then we got six. ADD six with one then we got seven. In 6 + 1 expression add six with one then we got seven. Both expressions are equal. So Lola is right.

c. Lola picked 9 + 7, and Charlie picked 15 – 8. Lola says these expressions are equal but Charlie disagrees. Who is right? Use a picture to explain your thinking.

Both expressions are not equal. Charlie is correct.
Explanation:
In the above image we can observe two expressions 9 + 7 and 15 – 8. In that expressions Lola picked 9 + 7 and Charlie picked       15 – 8. Lola says these expressions are equal, but Charlie disagrees. In 9 + 7 expression break seven into two parts as one and six. ADD one with nine then we got ten. ADD ten with six then we got sixteen. In 15 – 8 expression break fifteen into two parts as ten and five. Subtract eight from ten then we got two. ADD two with five then we got seven. Both expressions are not equal. So Charlie is right.

Question 3.
The following addition number sentences are FALSE. Change one number in each problem to make a TRUE number sentence, and rewrite the number sentence.

a. 10 + 5 = 9 + 5 __________________________

10 + 4 = 14
9 + 5 = 14
The number sentence is 10 + 4 = 9 + 5.
Explanation:
In the above image we can observe a number sentence 10 + 5 = 9 + 5. This number sentence is false. So we have to change one number to make a true number sentence. So cross out five and change it to four. In 9 + 5 expression break five into two parts as one and four. ADD nine with one then we got ten. ADD four with ten then we got fourteen. By adding ten and four expression results fourteen. Now both number sentences are equal.

b. 10 + 3 = 8 + 4 __________________________

10 + 2 = 12
8 + 4 = 12
The number sentence is 10 + 2 = 8 + 4.
Explanation:
In the above image we can observe a number sentence 10 + 3 = 8 + 4. This number sentence is false. So we have to change one number to make a true number sentence. So cross out three and change it to two. In 8 + 4 expression break four into two parts as two and two. ADD eight with two then we got ten. ADD two with ten then we got twelve. By adding ten and two expression results twelve. Now both number sentences are equal.

c. 9 + 3 = 8 + 5 __________________________