[tex]\left[\begin{array}{cc|c}-1&-1&-12\\-3&2&32\end{array}\right][/tex]
Multiply through row 1 by -1:
[tex]\left[\begin{array}{cc|c}1&1&12\\-3&2&32\end{array}\right][/tex]
Add 3(row 1) to row 3:
[tex]\left[\begin{array}{cc|c}1&1&12\\0&5&68\end{array}\right][/tex]
Multiply through row 2 by 1/5:
[tex]\left[\begin{array}{cc|c}1&1&12\\0&1&\frac{68}5\end{array}\right][/tex]
Add -1(row 2) to row 1:
[tex]\left[\begin{array}{cc|c}1&0&-\frac85\\&&\\0&1&\frac{68}5\end{array}\right][/tex]
