Answer
$1$
Work Step by Step
Using $P(n,r)=\dfrac{n!}{(n-r)!},$ the given expression, $P(
6,0
),$ evaluates to
\begin{array}{l}\require{cancel}
=\dfrac{6!}{(6-0)!}
\\\\=
\dfrac{6!}{6!}
\\\\=
\dfrac{\cancel{6!}}{\cancel{6!}}
\\\\=
1
\end{array}