Two angles of a triangle measure 55 degrees and 82 degrees. What is the measure of the third angle?

1. Let x equal the measure of the third angle. 2. The three angle measures must add to 180 degrees, so 55 plus 82 plus x equals 180. 3. Combine the known angles: 137 plus x equals 180. 4. Subtract 137 from both sides to get x equals 43 degrees. _Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 3 "Math Models", section 3.4 Solve Geometry Applications: Triangles, Rectangles, and the Pythagorean Theorem_