Multiply the top equation by 2 and combine both equations to leave x alone. It is better if you do this vertically but it is hard here.
(6x-2y=20)+(4x+2y=40)
10x=60
x=6
Plug x back in to one of the equations.
3(6)-y=10
18-y=10
-y=-8
y=8
Your solution is (6,8)
