Question

Сокращение доля:
1) 5 (x-y)
----------------
15 (y-x) 

Answer 1

$cfrac{5(x-y}{15(y-x)} =- cfrac{x-y}{3(x-y)} =- cfrac{1}{3}$

Answer 2

$frac{5(x-y)}{15(y-x)}=frac{-5(y-x)}{15(y-x)}=-frac{5}{15}=-frac13$