Question

What is the y-coordinate of the solution for the system of equations?

{x−y=12

27+3y=2x

Enter your answer in the box.

y =

Answer 1

First isolate either x or y in x - y = 12:
y = x - 12
Substitute x - 12 for y in 27 + 3y = 2x:
27 + 3(x - 12) = 2x
27 + 3x - 36 = 2x
-x = -9
x = 9
Substitue 9 for x in x - y = 12 and 27 + 3y = 2x
9 - y = 12 --> y = -3
27 + 3y = 2(9)
27 + 3y = 18
3y = -9
y = -3
So y = -3