Answer
$= \frac{9x^{2}-11}{x^{3}}$
Work Step by Step
1) Multiply a fraction with the other denominator to obtain a common denominator between the two fractions. In this case, we only need to multiply the first fraction by $x^{2}/x^{2}$ to get the common denominator of $x^{3}$
2) Subtract
$= \frac{9}{x} - \frac{11}{x^{3}}$
$ = \frac{9x^{2}}{x^{3}} - \frac{11}{x^{3}}$
$= \frac{9x^{2}-11}{x^{3}}$
