The above answers are correct. The following phrasing may make it clearer to some (it did for me, anyhow).

The problem is right here: the 3 men each paid $9 for the room. No they didn't. Each man paid $9 for the room (25) plus the bellboy's "tip" (2)--3x9=27=25+2. The other $3 of the original $30 are back in the men's pockets, each having $1.