Answer
$5x^{6}$
Work Step by Step
Based on the quotient rule for exponents, we know that $\frac{a^{m}}{{a}^{n}}=a^{m-n}, a\ne0$ (where $m$ and $n$ are positive integers and $a$ is a real number).
Therefore, $\frac{5x^{9}}{x^{3}}=5\times x^{9-3}=5\times x^{6}=5x^{6}$.