180°-75°- 40° =105°-40°=65°

180°-(75°+ 40°) =180°-105° =65°

65

180°-40°-60°=140°-60°=80°

180°-110°-55°=70°-55°=15°

180°-90°-55°=90°-55°=35°

90°-55°=35°