## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$x=12 ~or~x=-12$.
Using the definition of the absolute value, we have $$\frac{3}{4}|x|=9\Longrightarrow |x|=9\times\frac{4}{3}=12 .$$ Thus, we have the two possible solutions (negative and positive): $x=12 ~or~x=-12$.