Answer:the measure of angle 6 is 60 degrees.
Step-by-step explanation:
The two blue lines are straight and parallel lines. The sum of the angles on a straight line is 180 degrees. Angle 5 and angle 6 are on a straight line. Therefore
Angle 5 + angle 6 = 180
If angle 5 is 120 degrees, then
Angle 6 = 180 - 120 = 60 degrees.