My rings are 48, 36, and 26 - my freewheel is 12, 14, 16, 18, 21, 24, 28. I used Sheldon Brown's gear calculator here
http://sheldonbrown.com/gears/ to figure out what I was dealing with. The SRAM dual drive is one of the options in the dropdown boxes. Hope this helps. I can't figure out how to put a table into this message or I would show you my gear table, but you can do one for your bike and see exactly what you have.