How many ways can Jeff choose 4 shirts from a total of 13 shirts?
a) How many ways can Jeff choose 4 white shirts from 5 white shirts?
b) Given that Jeff has chosen a red shirt, how many ways are there for him to pick 3 shirts from the remaining 12?
c) We know it is certain that he will pack 0, 1, 2, 3, or 4 blue shirts. Let X be the event that he packs 0 blue shirts and Y be the event that he packs 1, 2, 3, or 4 blues shirts. So we know:
So now we need only compute the probability that he packs no blue shirts to answer the question.
So, how many ways are there to pick 4 shirts from the remaining 9 shirts?