This is a type of permutation problems in statistics. A permutation is a way in which the set of numbers can be arranged or order. In mathematics permutation relates to the act of ordering or arranging all the set of numbers into some sequence or order, or if the set is already in order or arranged its element the process is called permuting. Well, there are seven ways the first place can come in, then 6 ways for a second, and then 5 ways for third... so we multiply the 3 ways to get on how many different ways the first three finishers come in. 7*6*5 = 210 ways