Answer:
step 1. b = 102° (vertical angles)
step 2. one complete revolution equals 360°
step 3. a + b + c + 102 = 360
step 4. a + 102 + c + 102 = 360
step 5. a + c = 156°
step 6. 2a = 156 (vertical angles are equal)
step 7. a = 78°, c = 78°.
