solution tag is used to reveal the
answer to a question presented to the reader. The
problem and optional
solution tags appear inside the exercise
tag to present a question or task and an answer, respectively,
to the reader.
<exercise id="solutionexample">
<problem>
<para id="prob_1">
What is the capital of Texas?
</para>
</problem>
<solution>
<para id="sol_1">
Austin is the capital of Texas.
</para>
</solution>
</exercise>