Answer
$x=4$
Work Step by Step
Raising both sides to the third power of the given equation, $
\sqrt[3]{-4x-3}=\sqrt[3]{-x-15}
,$ then the solution/s is/are
\begin{array}{l}\require{cancel}
-4x-3=-x-15
\\\\
-4x+x=-15+3
\\\\
-3x=-12
\\\\
x=\dfrac{-12}{-3}
\\\\
x=4
.\end{array}