\(\dfrac{x}{2}=\dfrac{y}{3}\Rightarrow\dfrac{x}{10}=\dfrac{y}{15};\dfrac{y}{5}=\dfrac{z}{4}\Rightarrow\dfrac{y}{15}=\dfrac{z}{12}\\ \Rightarrow\dfrac{x}{10}=\dfrac{y}{15}=\dfrac{z}{12}\)
Áp dụng t/c dtsbn:
\(\dfrac{x}{10}=\dfrac{y}{15}=\dfrac{z}{12}=\dfrac{x+y-z}{10+15-12}=\dfrac{-26}{13}=-2\\ \Rightarrow\left\{{}\begin{matrix}x=-20\\y=-30\\z=-24\end{matrix}\right.\)