[tex]\it 1) \Delta=\left|\begin{array}{ccc}1&1\\ 1&2\end{array}\right| =2-1=1\\ \\ \\ \Delta _{x}=\left|\begin{array}{ccc}2&1\\ 1&2\end{array}\right| =4-1=3\\ \\ \\ \Delta _{y}=\left|\begin{array}{ccc}1&1\\ 2&1\end{array}\right| =1-2=-1[/tex]
[tex]\it x=\dfrac{\Delta_ x}{\Delta}=\dfrac{3}{1}=3\\ \\ \\ x=\dfrac{\Delta_ y}{\Delta}=\dfrac{-1}{1}=-1[/tex]
