9514 1404 393
Answer:
n = 16
Step-by-step explanation:
Angle ABC is the sum of its parts.
∠ABC = ∠ABF +∠FBC
159° = (7n +20)° +(2n -5)°
159° = 9n° +15° . . . . . . . . . . . . . . collect terms
144° = 9n° . . . . . . . . . . subtract 15°
16° = n°
n = 16
