If two angles are supplementary and one of them is 30, what is the measurement of the second angle?

A. 180

B. 90

C. 60

D. 150

You just need to know the definition of suplementary angles. Two angles are suplementary if the sum 180°. So, you now can easily deduct that the unkonwn angle is such that when sumed to 30° the result is 180° = > x + 30 = 180=> x = 180 - 30 = > x = 150°. And the answer is the option D) 150.