\(\begin{array}{l} \left\{ \begin{array}{l} \frac{7}{2}x - \frac{1}{3}y = - 6\\ \frac{1}{4}x + \frac{5}{6}y = - 3 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l} 21x - 2y = - 36\\ 3x + 10y = - 36 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l} x = \frac{{2y - 36}}{{21}}\\ 3\left( {\frac{{2y - 36}}{{21}}} \right) + 10y = - 36 \end{array} \right.\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \Leftrightarrow \left\{ \begin{array}{l} x = \frac{{2y - 36}}{{21}}\\ 72y = - 216 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l} x = - 2\\ y = - 3 \end{array} \right. \end{array}\)
Mình cứ rút x hoặc y rồi thế vào thôi bạn nhé =))