ZA and ZB are vertical angles. If mZA= (7x - 8) and m
ZB = (6x +17)", then find the value of x.

   Statement                  Reason        

1. AB = x + 16                 1. Given

  BC = 4x + 11

   AC = 77

2. AB + BC = AC             2. Segment Addition Postulate

3. x + 16 + 4x + 11 = 77     3. Substitution Property

4. 5x + 27 = 77                 4. Simplification (added like terms)

5. 5x = 50                         5. Subtraction Property of Equality

6. x = 10                             6. Division Property of Equality

7. AB = 10 + 16                   7. Substitution Property

8. AB = 26                          8. Simplification (added like terms)