Answer
$x=8, \quad y=-1 \quad z=8 $
Work Step by Step
In exercise $20,\ \quad A=\left[\begin{array}{lll}
5 & 7 & 4\\
3 & -1 & 3\\
6 & 7 & 5
\end{array}\right],$ we obtained
$A^{-1}=\left[\begin{array}{lll}
26 & 7 & -25\\
-3 & -1 & 3\\
-27 & -7 & 26
\end{array}\right]$
$B=\left[\begin{array}{l}
1\\
1\\
1
\end{array}\right],\quad X=\left[\begin{array}{l}
x\\
y\\
z
\end{array}\right]=A^{-1}B$
$X=\left[\begin{array}{lll}
26 & -7 & -25\\
-3 & -1 & 3\\
-27 & 7 & 26
\end{array}\right]\left[\begin{array}{l}
1\\
1\\
1
\end{array}\right]=\left[\begin{array}{l}
26+7-25\\
-3-1+3\\
-27-7+26
\end{array}\right]=\left[\begin{array}{l}
8\\
-1\\
-8
\end{array}\right]$
$x=8, \quad y=-1 \quad z=8 $
