Simplify the complex fraction below. Then supply the missing numerator.

$\displaystyle\frac{{\frac{{{x}-{5}}}{{{{x}}^{{2}}-{100}}}}}{{\frac{{{{x}}^{{2}}-{25}}}{{{2}{x}+{20}}}}}=\frac{?}{{{\left({x}-{10}\right)}{\left({x}+{5}\right)}}}\usepackage{cmbright}\Huge\$

The missing numerator is _____.