Answer:
12.
m∠ACB = 180° - 58° - 78° = 44°
m∠DCE = 180° - 85° - 60° = 35°
m∠BCD = 180° - 44° - 35° = 101°
13.
Base on the picture, we know that:
x° + 2x° + 3x° = 180°
6x° = 180°
x° = 180° ÷ 6 = 30°
=> m∠K = 2x° = 2 × 30° = 60°
=> m∠L = 3x° = 3 × 30° = 90°
=> m∠KML = x° = 30°
m∠LMN = 60° + 90° = 150°