Answer
Solution set = $\{(6,2)\}$
Work Step by Step
Reduce the augmented matrix $[A|B]$ to reduced row echelon form and interpret the result
$\left[\begin{array}{rr|r}
1 & 1 & 8\\
1 & -1 & 4
\end{array}\right]\rightarrow\left(\begin{array}{l}
.\\
R_{2}=r_{2}-r_{1}
\end{array}\right)$
$\rightarrow\left[\begin{array}{rr|r}
1 & 1 & 8\\
0 & -2 & -4
\end{array}\right]\rightarrow\left(\begin{array}{l}
.\\
R_{2}=r_{2}\div(-2)
\end{array}\right)$
$\rightarrow\left[\begin{array}{rr|r}
1 & 1 & 8\\
0 & 1 & 2
\end{array}\right]\rightarrow\left(\begin{array}{l}
R_{1}=r_{1}-r_{2}.\\
.
\end{array}\right)$
$\rightarrow\left[\begin{array}{rr|r}
1 & 0 & 6\\
0 & 1 & 2
\end{array}\right]$
The system is consistent and has a single solution.
$x=6,$
$y=2$
Solution set = $\{(6,2)\}$