Bài 2:
a.
\(\left\{\begin{matrix}
2x-3y=7\\
3x+2y=4\end{matrix}\right.\Leftrightarrow \left\{\begin{matrix}
x=\frac{3y+7}{2}\\
3x+2y=4\end{matrix}\right.\)
\(\Leftrightarrow \left\{\begin{matrix} x=\frac{3y+7}{2}\\ 3.\frac{3y+7}{2}+2y=4\end{matrix}\right.\)\(\Leftrightarrow \left\{\begin{matrix} x=\frac{3y+7}{2}\\ y=-1\end{matrix}\right.\Leftrightarrow \left\{\begin{matrix} x=2\\ y=-1\end{matrix}\right.\)
b,c bạn cũng làm tương tự.