Answer:
∠ 3 = 50°
Step-by-step explanation:
The exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
∠ 1 is an exterior angle of the triangle, so
90° + ∠ 3 = ∠ 1
90° + ∠ 3 = 140° ( subtract 90° from both sides )
∠ 3 = 50°
