Math Help - Permutations

1. Permutations

How many three letter combinations can be formed from the letters "defgh" if no letter can be used more than once.

I think this is the answer:

P(5!, 3!) = 5!/3! = 5 * 4 * 3! * 2!/3! * 2! = 5 * 4 = 20

Is this right?

2. If order matters, then P(5,3)=60.

If order doesn't matter, then C(5,3)=10

$P(n,k)=\frac{n!}{(n-k)!}$

$C(n,k)=\frac{n!}{(n-k)!k!}$