Hey, this may answer your question. By the way, this LaTeX code is easier t=
han the TeX code to implement you desires.
\section{Sixth try}
\newenvironment{ex}[2][]{
\begin{exercise}
\hskip1pt\par
#2 \par
#1}
{\end{exercise}}
\begin{ex}
{Mandantory part: This is only a question without a solution given.}
\end{ex}
\begin{ex}
[\noindent=E8=A7=A3=E7=AD=94{\bf \theexercise}\par An optional solution goe=
s here.]
{Mandentory part: This is only a question without a solution given.}
\end{ex}
An image is provided=20
http://ppt.cc/I7KA