Answer
The first step was wrong.
The correct answer is $x=3$.
Work Step by Step
The given function is $f(x)=4x+8$.
Substitute $f(x)=20$ into the function.
$20=4x+8$ This step is wrongly done by Ashlyn.
Subtract $8$ from both sides.
$20-8=4x+8-8$
Simplify.
$12=4x$
Divide both sides by $4$.
$\frac{12}{4}=\frac{4x}{4}$
Simplify.
$3=x$.
