i understand it mathematically, but just think about the scenario, whats wrong with the logic?
the bill is 25$, and we each pay 10 so the waitress has 30. she returns five $1 bills, each take one dollar, and leave the remaining 2 for her.
so now everyone has paid 10$ and got 1$ back, so they spent 9$, and the waitress got 2$. so to get the initial $30, we do ( 3 x 9)+2= 29 and not 30.
HOW DO YOU EXPLAIN THE SCENARIO, not mathematically, just follow the scenario and see where the fault with the logic is ( if any)