\(b,\left\{{}\begin{matrix}2x+y=3\\x-y=7\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}3x=10\\x-y=7\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{10}{3}\\\dfrac{10}{3}-y=7\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{10}{3}\\y=-\dfrac{11}{3}\end{matrix}\right.\)
\(c,\left\{{}\begin{matrix}2x-3y=6\\2x+y=3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}-4y=3\\2x+y=3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{-3}{4}\\2x-\dfrac{3}{4}=3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{-3}{4}\\x=\dfrac{15}{8}\end{matrix}\right.\)
b.
\(\left\{{}\begin{matrix}2x+y=3\\x-y=7\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}3x=10\\x-y=7\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{10}{3}\\\dfrac{10}{3}-y=7\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{10}{3}\\y=-\dfrac{11}{3}\end{matrix}\right.\)
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c.
\(\left\{{}\begin{matrix}2x-3y=6\\2x+y=3\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}-2x+3y=-6\\2x+y=3\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}4y=-3\\2x+y=3\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=-\dfrac{3}{4}\\2x-\dfrac{3}{4}=3\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}y=-\dfrac{3}{4}\\x=\dfrac{15}{8}\end{matrix}\right.\)
