Here's the question you clicked on:
sdk
Type the formula for the number of permutations of n things taken r at a time. p(n,r)=
\[ \frac {n!}{(n-r)!} \]
\( \color{Black}{\Rightarrow P(n,r) = \Large {n! \over (n - r)!} }\) lol had to give the answer out here.
Forgive me, Mr. Fool