Step-by-step explanation: Triangle ABC is an isosceles triangle, which means ∠C = ∠B. And the total degrees of a triangles inner angles is 180°. So to find ∠A all you do is 180° - (∠C + ∠B). ∠C + ∠B would be 30+30 which is 60° And 180° - 60° is 120°.