jessejess47: corret=correct ...sorry
No not true, because they didn't invest 9.
between 3 of them they paid 30, then 5 was taken out, so between 3 of them they had now paid 25, (30 -5 = 25). Then they each got 1 more back from the busboy, so add on 3 to the 25 and you get 28. Then the busboy got 2, and 28 +2 = 30.
Now if you divide (25+3), the 28 that they men had, by 3, you get 8.3, and 3x 8.3 =30, so no missing money.
You only assume that they got 9 each , when in fact they didn't.
They got one third of 25, + one dollar each, which = 9.3 dollars.