Hi Kevin,
>I am trying to frame a displaymath equation but I
>cannot compile.
>e.g $$a^m x a^n = a^{m+n}$$
>How can I frame this using \fbox command ??
How about:
$$
\fbox{$a^{m} \times a^{n} = a^{m+n}$}
$$
I believe that $$ is considered to be obsolete. You might want to use \[ and \] instead.
-Eddy