Dollar Missing

Can you help me to find my missing one dollar?
me and my two friends went to a hotel and had a meal.... at a total cost of a 30.
The hotel owner gave us a discount of 5. We accepted discount of 1 each and gave 2 dollar as tip to the waiter.
So, each of us put in 10 dollar.
and got one dollar back (10-1)*3=27,
we gave 2 dollar to the waiter.
27 plus 2 = 29 dollar. Where did the remaining one dollar go?
This is a very old riddle.
The simple answer is, you're doing the math wrong. When you calculated the amount you paid, you SUBTRACTED the amount you received back as a discount. But when you calculated the amount paid the waiter, you ADDED it. You should have subtracted it.
Original cost of meal: $30
Discount accepted: $3
Additional tip: $2
Amount owner received: 30 - 3 - 2 = 25.
The Missing Dollar