Answer
$720$
Work Step by Step
Using the order of operations on real numbers, the given expression, $
(-6)\cdot(-5)\cdot(-4)\cdot(-3)\cdot(-2)\cdot(-1)
,$ evaluates to
\begin{array}{l}\require{cancel}
30\cdot(-4)\cdot(-3)\cdot(-2)\cdot(-1)
\\\\=
-120\cdot(-3)\cdot(-2)\cdot(-1)
\\\\=
360\cdot(-2)\cdot(-1)
\\\\=
-720\cdot(-1)
\\\\=
720
.\end{array}