In order to find the value of x, consider that the measure of the angle above angle of 142° is equal to the measure of the angle with expression 2(x+9).
Take into account that the sum of the angle of 142° and the angle above it is equal to 180°.
Then, you have:
142 + 2(x + 9) = 180
solve the previous equation for x, as follow:
142 + 2(x + 9) = 180 apply distribution property left side
142 + 2x + 18 = 180 simplify like terms left side
2x + 160 = 180 subtract 160 left side
2x = 180 - 160
2x = 20
x = 20/2
x = 10
Hence. the value of x is 10°
