Answer
$\frac{x-5}{x}, with$ $x\ne0$
Work Step by Step
Given : $(\frac{x^{2}+x-6}{x^{2}-4x}) \times (\frac{x^{2}+x-20}{x^{2}+10x+25}) =\frac{(x-5)(x+5)}{x(x-4)} \times \frac{(x-4)(x+5)}{(x+5)(x+5)}=\frac{x-5}{x}$
(After dividing out the common factors (x-4) and (x+5))