Answer:
x = 140
Step-by-step explanation:
The left vertex in the triangle and 120° form a straight angle and are supplementary, thus
angle + 120° = 180° ( subtract 120 from both sides )
angle = 60°
The external angle of a triangle is equal to the sum of the 2 opposite interior angles.
x is an exterior angle to the triangle, thus
x = 80 + 60 = 140
