Solve the system by substitution. Check your solution.

a-1.2b=-3

0.2b+0.6a=12

A - 1.2b = - 3 ⇒ eq. 1

0.2b + 0.6a = 12 ⇒ eq. 2

a - 1.2b = - 3

a = 1.2b - 3 ⇒ eq. 3

Substitute eq. 3 to eq. 2

0.2b + 0.6 (1.2b - 3) = 12

0.2b +.72b - 1.8 = 12

Combine like terms

0.92b = 12 + 1.8

0.92b = 13.8 ⇒ divide both sides by 0.92 to get the value of b

b = 15

Substitute the value of b to eq. 3

a = 1.2b - 3

a = 1.2 (15) - 3

a = 15

to check: substitute the values of a and b to:

eq. 1

a - 1.2b = - 3

15 - (1.2) (15) = - 3

15 - 18 = - 3

- 3 = - 3 ⇒ correct!

eq. 2

0.2b + 0.6a = 12

(0.2) (15) + (0.6) (15) = 12

3 + 9 = 12

12 = 12 ⇒ correct!