3 guys order a family size pizza and each one pays $10. Therefore, the total for the pizza is $30.
The waiter realizes that he overcharged them knowing that the pizza costs $25. He takes $5 out of the cash register, keeps $2 in his own pocket and returns $1 to
each of the 3 guys.
Now, knowing that each of the 3 guys effectively paid each $9 for their share of the pizza and that the waiter kept $2 in his pocket, where did the remaining $1 disappear.
The math is 3 x $9 = $27 (effective payment by the 3 customers) + the $2 the waiter put in his pocket when he returned the overcharge amount
Therefore $27 paid + $2 in the pocket = $29. However, the original amount paid was $30. What happened to the last $1?