Question

http://prntscr.com/j7g2nh

Answer 1

@Vocaloid

Answer 2

@Shadow

Answer 3

Answer: A

Substitute y=3x-12
[2x-3(3x-12)=-13]


2x-3(3x-12)=-13
-3x(3x-12): -9x+36
-7x+36=-13 subtract 36 from both sides ( because you're doing the opposite of addition as shown) -7x+36-36=-13-36
solve: -7x = -49
Divide -7 to both sides -7x/7=-40/-7
Solve: 7

Now for y=3x-12
y=3*7-12
y=9

Now: x=7, y=9