Question

Solving liner system, substitution method 2x-y=23 x-9=-3

Answer 1

The easiest way to solve that would be elimination method, but if you have to do substitution:
x-9=-3
 add 9 to each side to get 
x=6
then plug 6 into the other equation for x
2(6)-y=23
and solve for y :)

Answer 2

2x - y = 23
x - 9 = -3

x - 9 = -3
  + 9  + 9
     x = 6
2(6) - y = 23
  12 - y = 23
- 12      - 12
       -y = 11
         y = -11
(x, y) = (6, -11)