Each triangle has a sum of angles that equal 180° so set each angle measure = 180
(x + 66) + (x + 86) + 50 = 180; add accordingly
2x + 202 = 180; subtract 202 from both sides
2x = -22; divide both sides by 2
x = -11
Plug in -11 for x to check
(-11 + 66) + (-11 + 86) + 50 = 180
55 + 75 + 50 = 180
180 = 180 so -11 is the correct value of x
