###### Item 1.2.5.2.a

This is not in reduced row echelon form since the leading entry in the second row is not the only nonzero entry in its column. Applying a replacement operation gives,

\begin{equation*}
\left[
\begin{array}{rrrr|r}
1 \amp 1 \amp 0 \amp 3 \amp 3 \\
0 \amp 1 \amp 0 \amp -2 \amp 1 \\
0 \amp 0 \amp 1 \amp 3 \amp 4 \\
\end{array}
\right]
\sim
\left[
\begin{array}{rrrr|r}
1 \amp 0 \amp 0 \amp 5 \amp 2 \\
0 \amp 1 \amp 0 \amp -2 \amp 1 \\
0 \amp 0 \amp 1 \amp 3 \amp 4 \\
\end{array}
\right]\text{.}
\end{equation*}

There are infinitely many solutions since \(x_4\) is a free variable.