Can somebody use elimination in this system of equation to solve it?
x-y = 4
x+3y =36

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  (12,8)