Answer
$\dfrac{x^{2}-2x+73}{(x-4)(x+1)(x+5)}$
Work Step by Step
$\dfrac{x+10}{x^{2}-3x-4}-\dfrac{8}{x^{2}+6x+5}-\dfrac{9}{x^{2}+x-20}$
Factor all three fractions completely:
$\dfrac{x+10}{(x-4)(x+1)}-\dfrac{8}{(x+5)(x+1)}-\dfrac{9}{(x+5)(x-4)}=...$
Evaluate the indicated operations and simplify:
$...=\dfrac{(x+10)(x+5)-8(x-4)-9(x+1)}{(x-4)(x+1)(x+5)}=...$
$...=\dfrac{x^{2}+15x+50-8x+32-9x-9}{(x-4)(x+1)(x+5)}=...$
$...=\dfrac{x^{2}-2x+73}{(x-4)(x+1)(x+5)}$