Answer
$17a+3x-21$
Work Step by Step
Using the Distributive Property and then combining like terms, the given expression, $
2a-3(-x-5a+7)
,$ simplifies to
\begin{array}{l}\require{cancel}
2a-3(-x)-3(-5a)-3(7)
\\\\=
2a+3x+15a-21
\\\\=
(2a+15a)+3x-21
\\\\=
17a+3x-21
.\end{array}