Question

If c and d are supplementary, and the measure of d is 45 what is the measure of c?

Answer 1

The definition of supplementary is that the angles add to 180°. Hence, c + d = 180; c + 45 = 180  by substitution and finally ∡c = 135°.

Answer 2

Supplementary angles are angles whose measures added together equals 180 degrees. To get angle c, subtract 45 from 180. This gives you 135, so the measure of angle C is 135 degrees.