## Introductory Algebra for College Students (7th Edition)

Supplementary angles are two angles, when added together, equal 180°. To find an angle's supplement, you subtract the measure of that angle from 180°. In other words, the measure of an angle's supplement can be found using the following formula, with $S$ as the measure of the supplementary angle and $x$ is the measure of the known angle: $$S = 180° - x$$