Giải thích các bước giải:
$\begin{array}{l}
1)\dfrac{x}{7} = \dfrac{y}{3}\\
\Rightarrow \dfrac{x}{7} = \dfrac{y}{3} = \dfrac{{x - y}}{{7 - 3}} = \dfrac{{x - \left( {x - 36} \right)}}{4} = 9\\
\Rightarrow \left\{ \begin{array}{l}
x = 9.7 = 63\\
y = 9.3 = 27
\end{array} \right.\\
\Rightarrow \left( {x;y} \right) = \left( {63;27} \right)
\end{array}$
Vậy $\left( {x;y} \right) = \left( {63;27} \right)$
$\begin{array}{l}
2)\dfrac{x}{3} = \dfrac{y}{5} = \dfrac{z}{7}\\
\Rightarrow \dfrac{x}{3} = \dfrac{y}{5} = \dfrac{z}{7} = \dfrac{{2x + 3y - z}}{{2.3 + 3.5 - 7}} = \dfrac{{ - 28}}{{14}} = - 2\\
\Rightarrow \left\{ \begin{array}{l}
x = - 2.3 = - 6\\
y = - 2.5 = - 10\\
z = - 2.7 = - 14
\end{array} \right.\\
\Rightarrow \left( {x;y;z} \right) = \left( { - 6; - 10; - 14} \right)
\end{array}$
Vậy $\left( {x;y;z} \right) = \left( { - 6; - 10; - 14} \right)$
