x = 40.

I created a third line that is parrellel to the first two. Then, I extended line GH.

Since vertical lines are congruent, the 80 degress reflects down. Then, using corresponding angles congruent, we have the angle next to the bottom 80 as 40.

Then, using corresponding angles again, we have x = 40.

Sorry, this might be confusing because I don't know how to make a picture.