assuming this is an augmented matrix, we could use say the variables of "x", "y" and "z" for it.
[tex]\bf \stackrel{augmented~matrix}{\begin{bmatrix}
0&1&2&\cdot &4\\
-2&3&6&\cdot &9\\
1&0&1&\cdot &3
\end{bmatrix}}\implies
\begin{cases}
0x+1y+2z=4\\
-2x+3y+6z=9\\
1x+0y+1z=3
\end{cases}
\\\\\\
\begin{cases}
y+2z=4\\
-2x+3y+6z=9\\
x+z=3
\end{cases}[/tex]
