Answer
$(-4,4)$
Work Step by Step
For any $a\gt0$, $|x|\lt a$ implies $-a\lt x\lt a$. (The symbol $\lt$ may be replaced with $\le$.)
Using the concept above, the solutions to the given inequality, $
| 5x|\lt20
,$ is
\begin{array}{l}\require{cancel}
-20\lt 5x\lt20
\\\\
-4\lt x\lt4
.\end{array}
In interval notation, the solution set is $
(-4,4)
.$
