Answer:
x = 9
Explanation:
Of course I'll do very simple explanation!
every time you see a straight line (nondiagonal) it measures 180°.
so if we're trying to solve for x in this case, we'll subtract 180° - 40° = 140°.
Then use the statement to solve for x

= - 50 Subtract 50 from both sides
90 Divide 10 from both sides
x = 9