### Home > GC > Chapter 2 > Lesson 2.1.2 > Problem 2-18

2-18.

**Examine** the diagrams below. What is the geometric relationship between the labeled angles? What is the relationship of their measures? Then, use the relationship to write an equation and solve for .

The labeled angles are vertical angles, so their measures are equal.

The labeled angles form a straight angle pair, so they are supplementary.