Nope. To find the difference, you would just subtract. The difference is 15dB (it's now a relative, unitless power measurement).
This is one of the big advantages of using dB as a measure -- you keep the slide rule off the desk. ;-)
By the way, occasionally some of the basic stuff gets lost in a corner if you haven't used it in a while. Sci.electronics.basics is anonymous, but you may wait a while for a correct answer, and there's always a chance that someone will throw a fly in the ointment. If you can't ask a co-worker, or if you're in a hurry, try the Wikipedia:
Although the articles are done by voluntary contributors, they're usually well-done, and if someone finds a problem, there's an easy way to resolve it by recommending an edit.