subtract the angle given by 180 because a straight angle is = to 180 so any number subtracted by 180 will give you the adjacent angle.
180-130=50
The angles inside a triangle when added are equal to 180. Since you just found out the angle measure in the uppermost corner which was 50. So now you subtract 50 from 180.
180-50= 130
You know that the y variable is congruent for both y's so they will have the same angle measure and you can divide the 130 by 2
