Answer
$\dfrac{3(x-4)}{5x} $
Work Step by Step
We apply Method 1 (A51), to treat the numerator and denominator of the complex rational expression separately. So by factoring both the denominator and numerator of each rational function and cancelling the common factors, we have
$$
\frac{\frac{12x}{5x+20}}{\frac{4x^2}{x^2-16}}= \frac{\frac{12x}{5(x+4)}}{\frac{4x^2}{(x+4)(x-4)}}= \frac{12x}{5(x+4)}\frac{(x+4)(x-4)}{4x^2}\\
=\frac{3(x-4)}{5x}
.$$
