They each SHOULD have paid $8.33333333333333. (*3=25).
They ACTUALLY paid $9, so they each paid $0.666666666 MORE than they should have.
This went to the bell boy as a tip (3*0.6666666666 = 2).
The hotel got $25, the men got $3 between them and the bell boy got $2 (25+3+2 = 30)
