Answer
$_{12}C_6=924$
Work Step by Step
$_nC_r=\frac{n!}{r!(n-r)!}$
$n=12$ and $r=6$
$_{12}C_6=\frac{12!}{6!(12-6)!}=\frac{12!}{6!\times6!}$
But, $12!=12\times11\times10\times9\times8\times7\times(6\times5\times4\times3\times2\times1)=12\times11\times10\times9\times8\times7\times6!$
$_{12}C_6=\frac{12\times11\times10\times9\times8\times7\times6!}{6!\times6!}=\frac{12\times11\times10\times9\times8\times7}{6\times5\times4\times3\times2\times1}=\frac{665,280}{720}=924$
