Ans.sty will very likely work with many other style files
besides the standard article.sty, but of course I can't
guarantee this. Since exersection uses subsection,
a different style file with a different definition of subsection
will place the exercise header in the same style as the other
subsections.
Prove that for any integer n > 2 there are no nonzero
integers x, y and z for which
xn + yn = zn.
If I knew how to do marginpar in LATEX I would
have written it in the margin. But that's the way the cookie
crumbles.
An exercise without an answer.
The very last exercise.
The very last answer.