\documentclass[12pt]{scrartcl}
\usepackage[LB]{spioncamp}
\newcommand{\kasten}[3]{\framebox{\vbox to #2 {\vfil\hbox to #1{#3}\vfil}}}
\geometry{}%doro left15mm}
\def\version{2 \today}

\begin{document}

\title{Modulo-Rechnung}
\subtitle{Schlüsselaustausch}
\hspace{-7ex}
\exercise{1}{
  \textbf{Berechne wie in den Beispielen auf dem Stationsblatt:}\\[1ex]
  
 \begin{tabular}{lrcrcrcrcrrrrcr}  
 ~ & $25$   & $mod$ & $  7$ & $=$ & \kasten{5mm}{5mm}{~4}  & , da & $ 25$ & $:$ & $ 7$ & $=$ & \kasten{5mm}{5mm}{~3} & \textbf{, Rest} & \kasten{5mm}{5mm}{~4}\\
 ~ & $90$   & $mod$ & $ 11$ & $=$ & \kasten{5mm}{5mm}{~2}  & , da & $ 90$ & $:$ & $11$ & $=$ & \kasten{5mm}{5mm}{~8} & \textbf{, Rest} & \kasten{5mm}{5mm}{~2}\\
 ~ & $23$   & $mod$ & $  8$ & $=$ & \kasten{5mm}{5mm}{~7}  & , da & $ 23$ & $:$ & $ 8$ & $=$ & \kasten{5mm}{5mm}{~2} & \textbf{, Rest} & \kasten{5mm}{5mm}{~7}\\
 ~ & $10$   & $mod$ & $ 19$ & $=$ & \kasten{5mm}{5mm}{10} & , da & $ 10$ & $:$ & $19$ & $=$ & \kasten{5mm}{5mm}{~0} & \textbf{, Rest} & \kasten{5mm}{5mm}{10}\\
 ~ & $106$  & $mod$ & $ 21$ & $=$ & \kasten{5mm}{5mm}{~1}  & , da & $106$ & $:$ & $21$ & $=$ & \kasten{5mm}{5mm}{~5} & \textbf{, Rest} & \kasten{5mm}{5mm}{~1}\\
 ~ & $42$   & $mod$ & $  4$ & $=$ & \kasten{5mm}{5mm}{~2}  & , da & $ 42$ & $:$ & $ 4$ & $=$ & \kasten{5mm}{5mm}{10} & \textbf{, Rest} & \kasten{5mm}{5mm}{~2}\\
 ~ & $8$    & $mod$ & $  3$ & $=$ & \kasten{5mm}{5mm}{~2}  & , da & $ 8$  & $:$ & $ 3$ & $=$ & \kasten{5mm}{5mm}{~2} & \textbf{, Rest} & \kasten{5mm}{5mm}{~2}\\
 ~ & $33$   & $mod$ & $ 15$ & $=$ & \kasten{5mm}{5mm}{~3}  & , da & \kasten{10mm}{5mm}{~~33}    & $:$ & \kasten{5mm}{5mm}{15} & $=$ & \kasten{5mm}{5mm}{~2} & \textbf{, Rest} & \kasten{5mm}{5mm}{~3}\\
 ~ & $107$  & $mod$ & $ 25$ & $=$ & \kasten{5mm}{5mm}{~7}  & , da & \kasten{10mm}{5mm}{~107}   & $:$ & \kasten{5mm}{5mm}{25} & $=$ & \kasten{5mm}{5mm}{~4} & \textbf{, Rest} & \kasten{5mm}{5mm}{~7}\\
 ~ & $2180$ & $mod$ & $ 54$ & $=$ & \kasten{5mm}{5mm}{28} & , da & \kasten{10mm}{5mm}{2180}  & $:$ & \kasten{5mm}{5mm}{54} & $=$ & \kasten{5mm}{5mm}{38} & \textbf{, Rest} & \kasten{5mm}{5mm}{28}\\
 ~ & $1011$ & $mod$ & $ 12$ & $=$ & \kasten{5mm}{5mm}{~3}  & , da & \kasten{10mm}{5mm}{1011}  & $:$ & \kasten{5mm}{5mm}{12} & $=$ & \kasten{5mm}{5mm}{84} & \textbf{, Rest} & \kasten{5mm}{5mm}{~3}\\
 ~ & $1001$ & $mod$ & $ 13$ & $=$ & \kasten{5mm}{5mm}{~0}  & , da & \kasten{10mm}{5mm}{1001}  & $:$ & \kasten{5mm}{5mm}{13} & $=$ & \kasten{5mm}{5mm}{77} & \textbf{, Rest} & \kasten{5mm}{5mm}{~0}\\ 
 ~ & $45$   & $mod$ & $ 14$ & $=$ & \kasten{5mm}{5mm}{~3}  & , da & \kasten{10mm}{5mm}{~~45}    & $:$ & \kasten{5mm}{5mm}{14} & $=$ & \kasten{5mm}{5mm}{~3} & \textbf{, Rest} & \kasten{5mm}{5mm}{~3}\\
 ~ & $785$  & $mod$ & $ 43$ & $=$ & \kasten{5mm}{5mm}{11} & , da & \kasten{10mm}{5mm}{~785}   & $:$ & \kasten{5mm}{5mm}{43} & $=$ & \kasten{5mm}{5mm}{18} & \textbf{, Rest} & \kasten{5mm}{5mm}{11}\\   
  \end{tabular}    
}

%\fbox{\parbox{\linewidth}{\vspace*{13cm}~}}

\end{document}