Question

Evaluate P(3, 0).

Answer 1

use the formula

P(n,r) = (n!)/(n-r)!

Answer 2

That's like saying, "In how many ways can 3 people sit in 0 chairs?" And of course, there's only one way: where they don't sit at all.
3! 3!
________ = ___ = 1
(3-0)! 3!
using this gives the same result