## College Algebra (6th Edition)

$\left\{\begin{array}{l} 3x=6\\ -3x+y=-7 \end{array}\right.$
The product on the LHS is between a 2$\times\underline{2}$ and a $\underline{2}\times$1 matrix, resulting in a 2$\times$1 matrix: $\left[\begin{array}{l} 3x+0y\\ -3x+y \end{array}\right]$ Equating matrices (equating corresponding elements), we have the system $\left\{\begin{array}{l} 3x=6\\ -3x+y=-7 \end{array}\right.$