Answer
$_8C_3=56$
Work Step by Step
RECALL:
$_nC_r = \dfrac{n!}{r!(n-r)!}$
Use this definition to have:
$\require{cancel}
_8C_3=\dfrac{8!}{3!(8-3)!}
\\_8C_3=\dfrac{8!}{3!(5!)}
\\_8C_3 = \dfrac{8(7)(6)(5!)}{3!(5!)}
\\_8C_3 = \dfrac{8(7)\cancel{(6)}\cancel{(5!)}}{\cancel{6}\cancel{(5!)}}
\\_8C_3=56$
