Answer
$n=10$
Work Step by Step
$_nP_r=\frac{n!}{(n-r)!}$, hence here the equation is: $\frac{n!}{(n-6)!}=5\frac{n!}{(n-5)!}$
If we multiply both sides by $(n-5)!=(n-5)\cdot(n-6)!$ we get: $n!(n-5)=5n!\\n-5=5\\n=10$
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