Answer:
a = 180° -73°
b = 73°
c = 180° -73°
Explanation:
73° and b are vertical angles, so are congruent (equal).
a and c are equal to each other and each is a linear angle with 73°, so is the supplement of that angle. You could write the equation as ...
a + 73° = 180°
but I prefer to get to the heart of it. The values of a and c are the difference between 180° and 73°.