Question

Help with geometry hw

Answer 1

A and a' are vertical angles, therefore a' = a

We know: The sum of the measures of triangle is always 180°.

Therefore: a' + b + d = 180° → d = 180° - a - b.

d and c are adjacent angles, therefore d + c = 180°

substitute

180° - a - b+ c = 180°    |-180°
-a - b + c = 0    |+a  |+b
c = a + b