Answer:
y=7-4x/-1
y=-7+4x
substituting y=-7+4x
-3x+4(-7+4x)=24
-3x-28+16x=24
-3x+16x-28-24=0
13x-52=0
13x=52
x=52/13
x=4
substituting x=4
-3x+4y=24
-3(4)+4y=24
-12-24+4y=0
-36+4y
4y=36
y=36/4
y=9
