Okay, (Assuming this is workings, dunno if it's the right method) multiply the bottom equation by -4 (for simplicity's sake here) so you get -4x+12y=12. (Changing the signs here) then to get rid of the x in the equation, add the two together.
4x-2y=8
+
-4x+12y=12
=
10y=20
Divide 20 by 10 to get y=2. then put the answer for y back into one of the equations.
x- 3(2)=-3
x-6=-3
x=3
in sum, y=2 and x=3.
That is how it's done, hope it helps:)