Answer:
100°
Step-by-step explanation:
Angles in a quadrilateral add up to equal 360
That being said we can calculate the measure of the missing angle by subtracting the measures of the known angles from 360
So missing angle = 360 - 120 - 100 - 40
360 - 120 - 100 - 40 = 100
Hence, the measure of the missing angle is 100°
