Answer
$_7P_3=210$
Work Step by Step
RECALL:
$_nP_r=\dfrac{n!}{(n-r)!}$
Use this to have:
$\require{cancel}\\_7P_3=\dfrac{7!}{(7-3)!}
\\_7P_3=\dfrac{7!}{4!}
\\_7P_3=\dfrac{7(6)(5)(4!)}{4!}
\\_7P_3=\dfrac{7(6)(5)\cancel{(4!)}}{\cancel{4!}}
\\_7P_3=210$
