Verified answer

11.1) (х+15+3х-5)=90;

4х=80; х=20;  

∠ВОС=20°+15°=35°;

∠АОС=3*20°-5°=55°

2)х+4х+30=90;

5х=60;

х=12;

∠АОС=12°;

∠ВОС=4*12°+30°=78°

3) 3х-35+2х+25=90;

5х=100;

х=20;

∠АОС=2*20°+25°=65°;

∠ВОС=3*20°-35°=25°