To use elimination for this, you would have to multiply everything by negative 1 for the first equation because x is not the opposite of the other x.
x-y=4
x+3y=36
-1(x-y)=4*-1
-x+y=-4
x+3y=36
NOW you can use elimination
4y=32
y=8
-x+8=-4
-x=-12
x=12
Final Answer: (12,8)
