Đáp án:
$\begin{array}{l}
x:y:z = 3:5:\left( { - 2} \right)\\
\Rightarrow \frac{x}{3} = \frac{y}{5} = \frac{z}{{ - 2}}\\
\Rightarrow \frac{x}{3} = \frac{y}{5} = \frac{z}{{ - 2}} = \frac{{5x}}{{15}} = \frac{y}{5} = \frac{{3z}}{{ - 6}} = \frac{{5x - y + 3z}}{{15 - 5 - 6}} = \frac{{186}}{4} = \frac{{93}}{2}\\
\Rightarrow \left\{ \begin{array}{l}
x = \frac{{93}}{2}.3 = \frac{{279}}{2}\\
y = \frac{{93}}{2}.5 = \frac{{465}}{2}\\
z = \frac{{93}}{2}.\left( { - 2} \right) = - 93
\end{array} \right.
\end{array}$
