Just fine. Internally geared hubs are usually built around the same technique as found in automatic transmissions for cars, with something called planetary gears.
what? there is no such as a 9 speed chain
OK, I don't know what this first "answer" was. To start from the beginning: there definitely IS such a thing as a 9-speed chain, just as there are 6-7...
Just write down exactly what you've included in the question, and eventually something will look promising: --> 7 minutes per mile --> 1 mile per 7 minutes = (1 mile) / (7 minutes) = (1/7)...