Answer
$3x^3-8x$
Work Step by Step
Recall the following rule: $\frac{a^{m}}{a^{n}}=a^{m-n}$
In order to solve this problem, use the rule above and cancel out common factors that are in both the numerator and the denominator of the fraction.
$=\dfrac{9x^6}{3x^3} - \dfrac{24x^4}{3x^3}
\\=3x^{6-3} - 8x^{4-3}
\\=3x^3-8x$