TeX source:

\begin{array}{crclllcc} \text{I} & 2x+6y &=& 14 \cr \text{II} & x+6y &=& 13 & \vert & -6y \cr \cr \text{I} & 2x+6y &=& 14 \cr \text{II} & x &=& 13-6y \cr \cr \text{II in I} & 2(13-6y)+6y &=& 14 \cr & 26-12y+6y &=& 14 & \vert & -26 \cr & -6y &=& -12 & \vert & :(-6) & \Rightarrow & y = 2 \cr \cr y=2 \text{ in II} & x &=& 13-6 \cdot 2 \cr & x &=& 13-12 & \Rightarrow & x = 1 \cr \cr & \mathbb{L} &=& \{\left(1; 2\right)\} \end{array}