#### Answer

$a=-\dfrac{21}{4}$

#### Work Step by Step

Using the properties of equality, the solution to the given equation, $
-\dfrac{8a}{7}-2=4
$, is
\begin{array}{l}
-\dfrac{8a}{7}=4+2
\\\\
-\dfrac{8a}{7}=6
\\\\
a=6\cdot\dfrac{-7}{8}
\\\\
a=-\dfrac{42}{8}
\\\\
a=-\dfrac{21}{4}
.\end{array}