$\begin{array}{l} D_h=\begin{array}{|cc|}a1\ & b1 \\ a2&b2 \\ \end{array}= a1 \cdot b2 -b1 \cdot a2 \\ D_x=\begin{array}{|cc|}c1\ & b1 \\ c2&b2 \\ \end{array}= c1 \cdot b2 -b1 \cdot c2 \\ D_y=\begin{array}{|cc|}a1\ & c1 \\ a2&c2 \\ \end{array}= a1 \cdot c2 -c1 \cdot a2\\ x=\frac{D_x}{D_h} \\ y=\frac{D_y}{D_h} \\ \\ \textbf{Gegeben:} \\ \\ 2 x +2 y =1\frac{7}{10}\\ 3 x +6 y = 3 \\ \\ \\ \\ \textbf{Rechnung:} \\ D_h=\begin{array}{|cc|}2\ & 2 \\ 3&6 \\ \end{array}= 2 \cdot 6 -2 \cdot 3=6 \\ D_x=\begin{array}{|cc|}1\frac{7}{10}\ & 2 \\ 3&6 \\ \end{array}= 1\frac{7}{10} \cdot 6 -2 \cdot 3=4\frac{1}{5} \\ D_y=\begin{array}{|cc|}2\ & 1\frac{7}{10} \\ 3&3 \\ \end{array}= 2 \cdot 3 -1\frac{7}{10} \cdot 3=\frac{9}{10} \\ \ x=\frac{4\frac{1}{5}}{6} \\ x=\frac{7}{10} \\ y=\frac{\frac{9}{10}}{6} \\ y=\frac{3}{20} \\ L=\{\frac{7}{10}/\frac{3}{20}\}\\ \, \end{array}$