Side BC of a triangle ABC has been produced to a point D such that ∠ACD = 120°. If ∠B = ∠A, then ∠A is equal to
By exterior angle theorem:
∠ACD = ∠A + ∠B
120o = ∠A + ∠A
120o =
240o = 3∠A
∠A = 80o