∠A - ∠B = 15 → ∠A = 15 + ∠B
∠B = ∠B
∠B - ∠C = 30 → ∠C = ∠B - 30
Since ABC is a triangle, then their sum equals 180°
∠A + ∠B + ∠C = 180
(15 + ∠B) + (∠B) + (∠B - 30) = 180
3∠B - 15 = 180
3∠B = 195
∠B = 65
∠A = 15 + ∠B → ∠A = 15 + 65 → ∠A = 80
∠C = ∠B - 30 → ∠C = 65 - 30 → ∠C = 35
Answer: ∠A = 80, ∠B = 65, ∠C = 35
