Question

-5x+8y=4. -x+y=7

Answer 1

-5x+8y=4
-5(-x+y=7)

-5x+8y=4
+5x-5y=-35
3y=-33
y=-11

-x+(-11)=7
-x-11=7
-x=18
x=-18

Answer 2

This is a system of equations. What you're going to want to do is multiply one of the equations by a number so one of the variables cancels out.

Answer 3

You solve for the variable that remains and then lug it into anyone of the original equations to solve for the other variable.