Evaluate the following expression. \[ { }_{9} P_{7} \]

Step 1 ：The given expression is a permutation, which is a way of arranging items where the order is important. In this case, we are asked to find the number of ways to arrange 7 items out of 9.

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 \(n!\) is the factorial of \(n\), which is the product of all positive integers up to \(n\).

Step 3 ：In this case, \(n = 9\) and \(r = 7\), so we need to calculate: \(P(9, 7) = \frac{9!}{(9-7)!}\)

Step 4 ：Final Answer: The value of the expression \({ }_{9} P_{7}\) is \(\boxed{181440}\)