Answer
$x\gt4$
Work Step by Step
In words the inequality is $x^3\gt4x^2\\x^3-4x^2=x^2(x-4)\gt0$
We know that $(x-k)^2\geq0$ for all $k$.
So here for the inequality to be true, $x-4\gt0\\x\gt4$ and $x^2\ne0\\x\ne0$
So the solution is $x\gt4$