Пусть х + у = 5 и z = –8. Найдите: x/(x+y+z).

\[\frac{z}{x + y + z} = \frac{- 8}{5 + ( - 8)} = \frac{- 8}{5 - 8} =\]

\[= \frac{- 8}{- 3} = \frac{8}{3} = 2\frac{2}{3}.\]