Question 1036645
.

y=x-12
y=4x  . Subtract this from above equation to eliminate y.
.
0=-3x-12 . Add 12 to each side
12=-3x . Divide each side by -3.
-4=x
.
y=4x=4(-4)=-16
.
---OR---
.
y=4x
y/4=x . Use this to substitute for x below
.
y=x-12 . Substitute for x from above
y=(y/4)-12 . Subtract (y/4) from each side
(4y/4)-(y/4)=-12
3y/4=-12 . Multiply each side by 4.
3y=-48 . Divide each side by 3.
y=-16
.
y=4x
-16=4x
-4=x
--------
ANSWER x=-4 and y=-16
.
CHECK:
.
y=x-12
-16=-4-12
-16=-16
.
y=4x
-16=4(-4)
-16=-16