Mathematics Homework Help

Mathematics Homework Help. How to figure out permutations, combinations and the fundamental counting principle

How many different ways can 28 runners place in an Olympic qualifying marathon?
If only the eight fastest runners advance to the Olympics; how many different ways can the eight fastest runners be chosen from the whole field of 28 runners?
If the runner in first place receives a gold medal, the runner in second place receives a silver medal, and the runner in third place receives a bronze medal, how many different ways can the three medalists be chosen from the entire field of 28 runners?