rule

Angle EOB+ Angle FOC= Angle EOB+ Angle EOG= = Angle Borg = = Angle OBC+ Angle OCB= (Angle ABC+ Angle ACB)/2 =( 180- Angle BAC)/2 = 120/2 = 60.

2. Let OB pass through AD to E, then the angle OED= = Angle A+ Angle OBA = 27+39/2 = 46.5.

So the angle O = 180- (angle OED+ angle ODA) =180-(46.5+27/2) =120.