Answer
$x=\dfrac{23}{3}$
Work Step by Step
$\bf{\text{Solution Outline:}}$
Using $f(x)=-\dfrac{3}{2}x+\dfrac{7}{2}$ from Exercise $80,$ replace $f(x)$ with $-8$ and then solve for $x.$
$\bf{\text{Solution Details:}}$
The expression $f(x)=-8$ means the value of $x$ when $f(x)$ is $-8.$ Replacing $f(x)$ with $-8$ and then solving for $x$ results to\begin{array}{l}\require{cancel}
f(x)=-\dfrac{3}{2}x+\dfrac{7}{2}
\\\\
-8=-\dfrac{3}{2}x+\dfrac{7}{2}
\\\\
2(-8)=2\left( -\dfrac{3}{2}x+\dfrac{7}{2} \right)
\\\\
-16=-3x+7
\\\\
3x=7+16
\\\\
3x=23
\\\\
x=\dfrac{23}{3}
.\end{array}
