Answer:
20
Explanation:
Straight line angles:
Angles on a straight line add up to 180°.
90 + 4x - 10 + x = 180
90 - 10 + 4x + x = 180
Combine like terms.
80 + 5x = 180
Subtract 80 from both sides,
5x = 180 - 80
5x = 100
Divide both sides by 5
x = 100 ÷ 5