Practice with the help of **Spectrum Math Grade 1 Answer Key Chapter 3 Lesson 3.15**** Using Addition and Subtraction**Â regularly and improve your accuracy in solving questions.

## Spectrum Math Grade 1 Chapter 3 Lesson 3.15 Using Addition and Subtraction Answers Key

**Think addition for subtraction. Solve each problem.**

Answer:

When seven is subtracted from twenty it gives the value 13 as shown below.

i.e.Â 20 -7 = 13

Answer:

Let the unknown number be x

7 + x = 20

x = 20 -7

x = 13

Therefore 7 + 13 is equal to 20.

Answer:

When seven is subtracted from Eighteen it gives the valueÂ 13 as shown below.

i.e.Â 18 -5 = 13

Answer:

Let the unknown number be x

5 + x = 20

x = 18 – 5

x = 13

Therefore 5 + 13 is equal to 18.

Answer:

When seven is subtracted from Nineteen it gives the value 12 as shown below.

i.e.Â 19 -7Â = 12

Answer:

Let the unknown number be x

7 + x = 19

x = 19 – 7

x = 12

Therefore 7 + 12 is equal to 19.

Answer:

When six is subtracted from seventeen it gives the value 11 as shown below.

i.e.Â 17 -6Â = 11

Answer:

Let the unknown number be x

6 + x = 17

x = 17 – 6

x = 11

Answer:

When four is subtracted from sixteen it gives the value 12 as shown below.

i.e.Â 16 – 4Â = 12

Answer:

Let the unknown number be x

4 + x = 16

x = 16 – 4

x = 12

Answer:

When one is subtracted from twelveÂ it gives the value 11 as shown below.

i.e.Â 12 – 1 = 11

Answer:

Let the unknown number be x

1 + x = 12

x = 12 – 1

x = 11

Answer:

When three is subtracted from fifteen it gives the value 12 as shown below.

i.e.Â 15 – 3 = 12

Answer:

Let the unknown number be x

3 + x = 15

x = 15 – 3

x = 12

Answer:

When three is subtracted from fifteen it gives the value 12 as shown below.

i.e.Â 14 – 3 = 11

Answer:

Let the unknown number be x

3 + x = 14

x = 14 – 3

x = 11

Answer:

When three is subtracted from fifteen it gives the value 12 as shown below.

i.e.Â 20 – 8 = 12

Answer:

Let the unknown number be x

8 + x = 20

x = 20 – 8

x = 12