Consider the figure:
If BC = AC, x = 2y, and angle ACB = 60o, then find the value of ∠A + ∠B + ∠x + ∠y (in degrees).
∠ACB = 60∘ and BC = AC,
∠A = ∠B [Angle opposite to equal sides are also equal]
By angle sum property of triangle, ∠A = ∠B = 60∘
x + y = ∠A + ∠B = 120∘ [Exterior angle property]
∠A +∠B +∠x +∠y = 60∘ +60∘ +120∘ = 240∘