∠AOC + ∠BOC = 120°
3∠BOC + ∠BOC = 120°
4∠BOC = 120°
∠BOC = 120° / 4 = 30°
∠AOC = 3 × 30° = 90°
∠AOB = 180° - ∠AOC = 180° - 90° = 90°
Ответ: ∠AOB = 90°, ∠BOC = 30°