Answer
840
Work Step by Step
Use the formula of permutation: $_{n}$P$_{r}$=$\frac{n!}{(n-r)!}$. Plug in 7 for N and 4 for R:
$_{n}$P$_{r}$=$\frac{n!}{(n-r)!}$
$_{7}$P$_{4}$=$\frac{7!}{(7-4)!}$ -simplify-
$_{7}$P$_{4}$=$\frac{7!}{3!}$ -write using factorial-
$_{7}$P$_{4}$=$\frac{7*6*5*4*3*2*1}{3*2*1}$ -simplify-
$_{7}$P$_{4}$=840
