Step-by-step explanation:
As we can see, the line on the bottom is a perfectly straight 180º line, so the two angles, a and 50º are supplementary angles. Remember: Supplementary angles = 180º, and complementary angles = 90º.
Since this is a 180º line, all we have to do is to subtract 50 from 180 to get our angle a.
180-50 = 130º
Our answer: a = 130º
