Please explain how you got your answer!

Answer: b =50°
Step-by-step explanation:
The angles on a straight line =180°
180° = 50°+90°+b
180°-50°-90°=b
50° = b
Answer:
Step-by-step explanation:
∠b + ∠a + 50° = 180°
∠b + ∠90 + 50° = 180°
∠b = 180° - 90° - 50° = 40°