In the given figure, calculate the value of angle q.

Since, AB is a straight line.

So,∠AOP + ∠POC + ∠COB = 180°

So, 50°+ x + 90° =180°

[∵ ∠AOP = 50° vertically opposite angles]

=» x +140° = 180°

=» x = 180°-140° = 40°

∵ q = x = 40° [vertically opposite angles]