Răspuns:
(<AOB)+(<BOC)+(<COA)=360°
2x+20°+3x+10°+4x+15°=360°
9x=360°-(20°+10°+15°)
9x=360°-45°
9x=315°
x=315°:9
x=35°
(<AOB)=35°×2+20°=90°
(<BOC)=35°×3+10°=115°
(<COA)=35°×4+15°=155°
(<BOM)=BOC:2=115:2=57°30'
(<CON)=(<COA):2=155°:2=77°30'
(<MON)=57°30'+77°30'=135°
