Đáp án:
`x/2=y/3=z/5` và `x.y.z=810`
`=>`$\left\{\begin{matrix} 5x-2y=0\\ 5y-3z=0 \\xyz=810\end{matrix}\right.⇔\left\{\begin{matrix} x=\dfrac{2}{3}y\\ z=\dfrac{5}{3}y \\\dfrac{2}{3}y.y.\dfrac{5}{3}y=810\end{matrix}\right.⇔\left\{\begin{matrix} x=\dfrac{2}{3}y=6\\ z=\dfrac{5}{3}y=15 \\y=9\end{matrix}\right.$