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Row reduction of the augmented matrix
2x-y=7
3x+4y=-6

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\left[\begin{array}{ccc}2x - y\\3x + 4y\end{array}\right] = \left[\begin{array}{ccc}7\\-6\end{array}\right]

\left[\begin{array}{ccc}2&-1\\3&4\end{array}\right]\left[\begin{array}{ccc}x\\y\end{array}\right] = \left[\begin{array}{ccc}7\\-6\end{array}\right]

\left[\begin{array}{ccc}x\\y\end{array}\right] = (1)/(11)\left[\begin{array}{ccc}4&1\\-3&2\end{array}\right]\left[\begin{array}{ccc}7\\-6\end{array}\right] = (1)/(11)\left[\begin{array}{ccc}22\\-33\end{array}\right] = \left[\begin{array}{ccc}2\\-3\end{array}\right]

(x, y) = (2, -3)
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