###### Item1.2.5.1.b

The reduced row echelon form is

\begin{equation*} \left[\begin{array}{rrr|r} 1 \amp 0 \amp 0 \amp -1 \\ 0 \amp 1 \amp 0 \amp 0 \\ 0 \amp 0 \amp 1 \amp 1 \\ \end{array}\right]\text{.} \end{equation*}

All the variables are basic so there is a unique solution: $$x_1 = -1\text{,}$$ $$x_2=0\text{,}$$ and $$x_3=1\text{.}$$

in-context