\documentclass{handout}
\setlength\parindent{0pt}
\begin{document}
\section*{Strahlensatz}
\begin{Aufg}
\includegraphics[keepaspectratio, width=0.8\textwidth]{Copyrighted/Fokus9_S91_A12.png}
\end{Aufg}

\begin{Lsg}
\includegraphics[keepaspectratio, width=\textwidth]{Copyrighted/Fokus9_S91_A12_Lsg.png}
\end{Lsg}

\begin{Aufg}
\includegraphics[keepaspectratio, width=0.8\textwidth]{Copyrighted/Fokus9_S92_A16.png}
\end{Aufg}

\begin{Lsg}
\includegraphics[keepaspectratio, width=\textwidth]{Copyrighted/Fokus9_S92_A16_Lsg.png}
\end{Lsg}
\end{document}

\begin{Lsg}
\includegraphics[keepaspectratio, width=\textwidth]{Copyrighted/FokusS168_A21_Lsg.png}
\end{Lsg}