Help me with this riddle...

I was told the old “Sailors and the lost money” riddle a few years ago. I never could figure it out. Imagine my joy when finding Cecil figure it out for me. http://www.straightdope.com/classics/a910621.html
Great! I even printed it out to show my BF. The only problem is…I don’t quite understand how Cecil explained it.I get the general point, but I don’t understand how he got there. Anybody can explain it to me in more clear terms? Right now it’s about as clear as mud!

“Everybody’s got something to hide except for me and my monkey”-The Beatles
“People try to tell me thoughts they cannot defend…” The Moody Blues
“To start, press any key. Where’s the any key?” Homer Simpson.

You don’t add the two dollars the bellhop kept. That two dollars is part of the 27 dollars (3 times 9) paid by the sailors. The three dollars returned as change makes the thirty dollars originally paid.

3 x 10 = 25(for the room) + 2(kept by bellhop) + 3(change returned to sailors)

QED

There was a thread discussing this riddle here.