Answer:
Explanation:
You are using the wrong accounting system
Forget the nine dollars.
If the thing bought was 25 dollars, then each one of A B and C put in 25/3 = 8.3333 dollars. If 1 dollar each was going back, then the sum became 9 1/3 dollars. 3 * 9 1/3 = 27 + 1 = 28. There is 2 dollars left. Everything is fine.
25 + 3 = 28
The three each got 1 dollar back. But the total accounted for is 25 + 3 = 28
There's 2 left over. That makes 30. Everything's fine. There is no missing dollar.