Answer:
X=20
Step-by-step explanation:
When you add 7x and the x+20, they total to 180 degrees to form a flat angle so to solves this use equation 7x+x+20=180 to get x=20.
To check: input the 20 into both equations and see if they add up to 180 degrees
7x20=140
20+20= 40
140+40= 180
