Here is the code:
\documentclass{article}
\usepackage[vmargin=1in]{geometry}
\usepackage{xfrac,fontspec,unicode-math}
\setmathfont[version=lm]{Latin Modern Math}
\setmathfont[version=cambria]{Cambria Math}
\usepackage{xgreek}
\usepackage{exsheets}
\begin{document}
\setmainfont{Latin Modern Roman}
\mathversion{lm}
\section*{Latin Modern}
There follows a question
\begin{question}
This is the first question
\end{question}\\
\begin{question}[name=Problem]
This is the second question
\end{question}
\setmainfont{Cambria}
\mathversion{cambria}
\section*{Cambria, Cambria Math}
There follows a question
\begin{question}
This is the first question
\end{question}\\
\begin{question}[name=Problem]
This is the second question
\end{question}
\end{document}
and the output is
Does anybody has a solution?
*Exsheets works fine with xelatex if unicode-math is not in the preamble
\AtBeginDocument{\RenewQuSolPair{question}{solution}}
(in the preamble) works for me. By the way: the\` after
\end{question}` is wrong... – cgnieder Nov 23 '13 at 10:33\\
after\end{question}
« – cgnieder Nov 23 '13 at 10:46