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

Think addition for subtraction. Solve each problem.

When seven is subtracted from twenty it gives the value 13 as shown below.
i.e.Â  20 -7 = 13

Let the unknown number be x
7 + x = 20
x = 20 -7
x = 13
Therefore 7 + 13 is equal to 20.

When seven is subtracted from Eighteen it gives the valueÂ  13 as shown below.
i.e.Â  18 -5 = 13

Let the unknown number be x
5 + x = 20
x = 18 – 5
x = 13
Therefore 5 + 13 is equal to 18.

When seven is subtracted from Nineteen it gives the value 12 as shown below.
i.e.Â  19 -7Â  = 12

Let the unknown number be x
7 + x = 19
x = 19 – 7
x = 12
Therefore 7 + 12 is equal to 19.

When six is subtracted from seventeen it gives the value 11 as shown below.
i.e.Â  17 -6Â  = 11

Let the unknown number be x
6 + x = 17
x = 17 – 6
x = 11

When four is subtracted from sixteen it gives the value 12 as shown below.
i.e.Â  16 – 4Â  = 12

Let the unknown number be x
4 + x = 16
x = 16 – 4
x = 12

When one is subtracted from twelveÂ  it gives the value 11 as shown below.
i.e.Â  12 – 1 = 11

Let the unknown number be x
1 + x = 12
x = 12 – 1
x = 11

When three is subtracted from fifteen it gives the value 12 as shown below.
i.e.Â  15 – 3 = 12

Let the unknown number be x
3 + x = 15
x = 15 – 3
x = 12

When three is subtracted from fifteen it gives the value 12 as shown below.
i.e.Â  14 – 3 = 11

Let the unknown number be x
3 + x = 14
x = 14 – 3
x = 11