Explanation:
For the triangle on the bottom right the missing angle is
180- (74+50)= 56°
For the triangle on the bottom left the missing angle is
180- (45+80)= 55°
For the triangle in the middle the missing angle is
180- (54+51)= 75°
For the triangle on top the missing angle is
180- (80+54)= 46°
180- (74+51)= 55°
180- (46+55)= 79°