The trifecta at most racetracks consists of selecting the first-, second-, and third-place finishers in a particular race in their proper order. If there are eight entries in the trifecta race, how many tickets must you purchase to guarantee a win? You must purchase tickets.

Step 1 ：This is a permutation problem. In a permutation, the order of the items is important. In this case, we are selecting 3 horses out of 8, and the order in which they finish is important.

Step 2 ：The formula for permutations is: \(P(n, r) = \frac{n!}{(n-r)!}\) where n is the total number of items, r is the number of items to choose, and '!' denotes factorial, which is the product of all positive integers up to that number.

Step 3 ：In this case, n = 8 (the total number of horses) and r = 3 (the number of horses to choose for first, second, and third place).

Step 4 ：Substituting the values into the formula, we get \(P(8, 3) = \frac{8!}{(8-3)!}\)

Step 5 ：Solving the above expression, we get the number of tickets as 336.0

Step 6 ：Final Answer: You must purchase \(\boxed{336}\) tickets.