Answer
$x=-400/3, \quad y=-700/3 $
Work Step by Step
In exercise 14, $\quad A=\left[\begin{array}{ll}
-7 & 4\\
8 & -5
\end{array}\right],$ we obtained
$A^{-1}=\left[\begin{array}{ll}
-5/3 & -4/3\\
-8/3 & -7/3
\end{array}\right]$
$B=\left[\begin{array}{l}
0\\
100
\end{array}\right],\quad X=A^{-1}B$
$X=\left[\begin{array}{ll}
-5/3 & -4/3\\
-8/3 & -7/3
\end{array}\right]\left[\begin{array}{l}
2\\
20
\end{array}\right]=\left[\begin{array}{l}
-5/3(0)-4/3(100)\\
-8/3(0)-7/3(100)
\end{array}\right]=\left[\begin{array}{l}
-400/3\\
-700/3
\end{array}\right]$
$x=-400/3, \quad y=-700/3 $
