#### Answer

$f(8)=-\dfrac{17}{2}$

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
Use $f(x)=-\dfrac{3}{2}x+\dfrac{7}{2}$ from Exercise $80.$ Then replace $x$ with $8$ to find $f(8).$
$\bf{\text{Solution Details:}}$
Replacing $x$ with $8$ in $f(x)=-\dfrac{3}{2}x+\dfrac{7}{2}$ results to
\begin{array}{l}\require{cancel}
f(x)=-\dfrac{3}{2}x+\dfrac{7}{2}
\\\\
f(8)=-\dfrac{3}{2}(8)+\dfrac{7}{2}
\\\\
f(8)=-\dfrac{24}{2}+\dfrac{7}{2}
\\\\
f(8)=-\dfrac{17}{2}
.\end{array}