It's difficult to ascertain exactly what you're asking here. Is "9 less than m" part of an equation you're trying to work out, or part of an inequality, or?
If you're simply asking how to write 9 less than m, that would be m-9. In my experience, word problems containing 'something less than something else' prove to be confusing for students, because one automatically thinks the second term stated should be subtracted from the first. It is the other way around, however.
Here are some other examples to help make it clearer:
8 less than x: x-8
4 less than 6: 6-4
3 less than y-6: (y-6)-3
If this didn't help you at all, please provide more information on what you are looking to figure out, and we'll go from there.