Answer:
x=20
Step-by-step explanation:
The lines on the top and bottom are shown to be parallel and the line in between is a transversal. This means that the same side interior theorem applies. The same side interior theorem states that 2 angles on the same side of a transversal, inside 2 parallel lines will sum 180 degrees.
So, to solve, add the expressions together and set them equal to 180.
80+(4x+20)= 180
4x+100=180
4x=80
x=20