Find the number of ways to select 3 different letters from the set .
How many teams of four can be selected from a group of 20 people?
A team of four is to be randomly selected from a group of ten boys and ten girls. Determine the probability that a team will contain only girls.
Seven boys and eight girls entered a draw for four free movie tickets. What is the probability that all four tickets were won by boys?
Which of the following represents the number of ways of selecting 2 students out of 24 for a class activity?