∠d and ∠70° are vertical angles.
Vertical angles are equal. Therefore m∠d = 70°.
∠a and ∠70°, ∠a and ∠b, ∠c and ∠b, ∠c and ∠d are complementary angles.
The sum of measures the two complementary angles is 90°. Therefore
m∠a = 90° - 70° = 20°
m∠b = 90° - 20° = 70°
m∠c = 90° - 70° = 20°
m∠d = 90° - 20° = 70°
