Answer
$-21n+36$
Work Step by Step
Removing the grouping symbol and then combining like terms, the given expression, $
3[4n-5(2n-1)]-3(n-7)
$, simplifies to
\begin{array}{l}\require{cancel}
3[4n-10n+5]-3n+21
\\\\=
3[-6n+5]-3n+21
\\\\=
-18n+15-3n+21
\\\\=
(-18n-3n)+(15+21)
\\\\=
-21n+36
.\end{array}
