Answer
$-\displaystyle \frac{132}{33}$
Work Step by Step
$\left[\begin{array}{lll}
\text{What number} & \rightarrow & x...\\\\
\text{multiplied by the numerator and } & & \\
\text{subtracted from the denominator of }\dfrac{9}{11} & \rightarrow & \dfrac{9x}{11-x} \\ \\
\text{makes fraction... equivalent to }-\dfrac{12}{5} & \rightarrow & =-\dfrac{12}{5}
\end{array}\right]$
$\displaystyle \frac{9x}{11-x}=-\frac{12}{5}\qquad/...\times 5(11-x)$
$9x(5)=-12(11-x)$
$45x=-132+12x\qquad/...-12x$
$33x=-132\qquad/...\div 33$
$x=-\displaystyle \frac{132}{33}$
