XSL mathematics: is this possible?

[Mr Initial Man]

I'm doing an XML file with the output as a table. Unfortunately, I've run into a problem.

What I'm wondering is if the following is possible: to add one to a numeric attribute from the XML file using XSLT.

[Stephen Philbin]

Im sure I remember reading something like that in one of the XML related recommendations (I'm pretty sure it was XSL-T).