#1. <1=<ABC=50°

<BCA=180°-134°=46°

<A=180°-(50°+46°)=64°

#2. 2x+5x+8x=180°

15x=180°

x=180°:15

x=12°

Наименьший угол 12°×2=24°

#3. <OAB=50°÷2=25

<OBA=60°÷2=30°

<AOB=180°-(30°+25°)=125°

#4. <BCA=180°-140°=40°

3x+4x+40°=180°

7x+40°=180°

7x=180°-40°

7x=140°

x=140°÷7

x=20°

<A=3×20°=60°

<B=4×20°=80°

<C=40°