Answer
$-16a+27b-32c$
Work Step by Step
Using $a(b+c)=ab+ac$ or the Distributive Property, the given expression, $
4a-b-4(5a-7b+8c)
$, is equivalent to
\begin{array}{l}\require{cancel}
4a-b-4(5a)-4(-7b)-4(8c)
\\\\=
4a-b-20a+28b-32c
.\end{array}
By combining like terms, then this simplifies to
\begin{array}{l}\require{cancel}
(4a-20a)+(-b+28b)-32c
\\\\=
-16a+27b-32c
.\end{array}