Ответ:

1/4x+105°+1/3x+40°=180°

7/12x=180°-145°

7/12x=35°

x=35°×12/7

x=60°

2)2x-55°=1/3x+45°

2x-1/3x=55+45

1 2/3x=100°

x=100°×3/5

x=60°

3)1/3x+95°+2x-20°=180°

2 1/3x=180-75

7/3x=105°

x=105°×3/7

x=45°

4)x+45°=1/4x+105°

x-1/4x=105-45

3/4x=60°

x=60×4/3

x=80°