Question

Triangle ABC and triangle BDE share a vertex at point B, as shown. What is

the measure, in degrees, of angle A?*
​

Answer 1

The measure of angle A is 30 degrees

Explanation:

The addition of the three angles of a triangle must be equal to 180°. Therefore:

∠B + ∠D + ∠E = 180°

∠B + 70° + 50° = 180°

∠B = 180° - 70° - 50°

∠B = 60°

∠B + ∠C + ∠A = 180°

60° + 90° + ∠A° = 180°

∠A = 180° - 90° - 60°

∠A = 30°