Answer
Solution set = $\{(2,-1)\}$
Work Step by Step
$D= $determinant of the coefficient matrix
$=\left|\begin{array}{ll}
2 & 1\\
1 & -1
\end{array}\right|=2(-1)-1(1)=-3$
$D_{x}=$ in D, replace the x column with the constants column
$= \left|\begin{array}{ll}
3 & 1\\
3 & -1
\end{array}\right|=3(-1)-1(3)=-6$
$D_{y}=$ in D, replace the x column with the constants column
$=\left|\begin{array}{ll}
2 & 3\\
1 & 3
\end{array}\right|=6-3=3$
$x=\displaystyle \frac{D_{x}}{D}=\frac{-6}{-3}=3$
$y=\displaystyle \frac{D_{y}}{D}=\frac{3}{-3}=-1$
Solution set = $\{(2,-1)\}$
