Question:
A bag contains 5 white and 7 red balls. One ball is drawn at random. What is the probability that ball drawn is not black?
Solution:
GIVEN: A bag contains 7 red, and 5 white balls and a ball is drawn at random
TO FIND: Probability that the ball drawn is white
Total number of balls 
Total number of white balls is 5
We know that PROBABILITY = 
Probability of getting a white ball 