4x-y=20 and - 2x-2y=10

You can use Substitution to solve this problem:

4x-y=20

-y=-4x+20

y=4x-20

Now you have two equations, and you use the first one to substitute into the second one.

y=4x-20 and - 2x-2y=10

-2x-2 (4x-20) = 10

-2x-8x+40=10

-10x+40=10

-10x=-30

-x=-3

x=3

Now that we have figured out what x is, we can substitute x in to one of the equations to figure out y.

4x-y=20 x=3

4 (3) - y=20

12-y=20

-y=8

y=-8

So your answer would be x=3 and y=-8