Answer
$x=-38, \quad y=9\quad z=47 $
Work Step by Step
In exercise 14, $\quad A=\left[\begin{array}{lll}
2 & 4 & 1\\
-1 & 1 & -1\\
1 & 4 & 0
\end{array}\right],$ we obtained
$A^{-1}=\left[\begin{array}{lll}
-4 & -4 & 5\\
1 & 1 & -1\\
5 & 4 & -6
\end{array}\right]$
$B=\left[\begin{array}{l}
7\\
0\\
-2
\end{array}\right],\quad X=\left[\begin{array}{l}
x\\
y\\
z
\end{array}\right]=A^{-1}B$
$X=\left[\begin{array}{lll}
-4 & -4 & 5\\
1 & 1 & -1\\
5 & 4 & -6
\end{array}\right]\left[\begin{array}{l}
7\\
0\\
-2
\end{array}\right]=\left[\begin{array}{l}
-4(7)-4(0)+5(-2)\\
1(7)+1(0)-1(-2)\\
5(7)+4(0)-6(-2)
\end{array}\right]=\left[\begin{array}{l}
-38\\
9\\
47
\end{array}\right]$
$x=-38, \quad y=9\quad z=47 $
