Đáp án:
\(\left\{ \begin{array}{l}
y = - \dfrac{{90}}{{59}}\\
x = - \dfrac{{70}}{{59}}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
\left\{ \begin{array}{l}
\dfrac{x}{y} = \dfrac{7}{9}\\
3x - 22y = 30
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = \dfrac{7}{9}y\\
3.\dfrac{7}{9}y - 22y = 30
\end{array} \right.\\
\to \left\{ \begin{array}{l}
\left( {\dfrac{7}{3} - 22} \right)y = 30\\
x = \dfrac{7}{9}y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - \dfrac{{90}}{{59}}\\
x = - \dfrac{{70}}{{59}}
\end{array} \right.
\end{array}\)
