A bag contains 5 red, 8 green and 7 white balls. One ball is drawn at random from the bag. What is the probability of getting a white ball or a green ball?
Total numbers of elementary events are: 5+8 + 7 = 20
Let E be the event of getting a green ball or a white ball
Total numbers of favorable outcomes are: 8+ 7 = 15
P (white or green ball) = P (E) = 15/20 = 3/4