Solve the system by substitution.

Question

x + 3y = –4 and 2x + 2y = –8?

Answer 1

x + 3y = –4  ------(1)

2x + 2y = –8  -----(2)

Add  -3y to both sides to the eqation (1)

x + 3y -3y  = –4 -3y

x = - 4 - 3y

Now substitute    x = - 4 - 3y    in eqation (2)

          2 (- 4 - 3y) + 2y = -8

          -8 - 6y +2y = -8

          -8 - 4y = -8

          -8 -4y +8 = -8 +8

           -4y = 0

            y = 0

Now substitute y =0 in eqation (1)

        x +3(0) = -4

          x= -4

The values of x and y are   -4, 0  respectively