Answer
The answer is $\left[\begin{array}{ccc|c}
1& -4 & 2&3 \\
1 &-4 &4&0 \\
2&0&7&4\\
\end{array}\right]$.
Work Step by Step
The given matrix is
$\left[\begin{array}{ccc|c}
3 & -12 & 6&9 \\
1 &-4 &4&0 \\
2&0&7&4\\
\end{array}\right]$
Perform $\frac{1}{3}R_1 $
Multiply row one by $ \frac{1}{3} $
$\left[\begin{array}{ccc|c}
3\cdot \frac{1}{3}& -12\cdot \frac{1}{3} & 6\cdot \frac{1}{3}&9\cdot \frac{1}{3} \\
1 &-4 &4&0 \\
2&0&7&4\\
\end{array}\right]$
Simplify.
$\left[\begin{array}{ccc|c}
1& -4 & 2&3 \\
1 &-4 &4&0 \\
2&0&7&4\\
\end{array}\right]$
