A bag contains 9 identical balls out of which 3 are blue, 2 are white and the remaining are red. If a ball is drawn from the bag what is probability that it is :
1. blue
2.not red.​

Total number of balls  = 9

answer: option a.

step-by-step explanation:

you know that the quadrilateral opqr ( a four sided figure) is inscribed in circle. this means that all its vertices are on the circle.

then, by definition, the opposite angles of the quadrilateral are supplementary, this means that the sum of their measures is 180 degrees.

you can observe in the figure that the angles ∠opq   and the angle ∠orq   are opposite, therefore:

then, can be used to d to calculate the measure of ∠opq