Try this LaTeX code:

\begin{matrix} \begin{array}{|l|} \hline equation_1 \\ equation_2 \\ equation_3 \\ equation_4 \\ equation_5 \\ \hline \end{array} & (EUL) \end{matrix}

yields:

This is a 1x2 matrix with the first cell consisting of an array that has been defined with vertical and horizontal lines, and the second cell is the tag that you specified.