### Home > GC > Chapter 7 > Lesson 7.1.1 > Problem 7-7

7-7.

Refer to the Math Notes box in Lesson 2.1.4 if you need help establishing any angle pair relationship.

Since the highlighted angles are vertical angles, and vertical angles are equal,

Use the Triangle Angle Sum Theorem to calculate :

To find *,* notice that it is the exterior angle in the small triangle that contains