### Home > GB8I > Chapter 9 Unit 3 > Lesson CC3: 9.2.2 > Problem 9-79

9-79.

Calculate the value of .

An exterior angle of a triangle is equal to the sum of the two remote interior angles.

Notice that the

angle corresponds to the angle adjacent to angle . This angle is complementary to angle.The vertical angle is equal to the

angle because they are alternate interior angles on parallel lines.