Dave
You of course know that you should never use tables for layout purposes ....but....maybe the easiest way is to use a table.
You can see how I laid out a calc and another widget horizontally here:
(login: admin password: googlepoodll )
http://demo.poodll.com/mod/page/view.php?id=94
Choose to edit the activity and you will see exactly how I did it in TinyMCE.
Justin