<h1>Where did the dollar go?Math brain teaser</h1>

3 friends went to the restaurant, the account was $ 30 and they each gave $ 10.

The waiter gave them a $ 5 change, of which they each received $ 1 and gave a tip
 of $ 2.


But in the end they think: We each gave $10  and got 1 back, so everyone paid $ 9 . Three times 9 makes us 27 and  $ 2 for the tip, 29. Where did the dollar go?

 It's an old math puzzle that confuses many people.
 In order to answer this logic puzzle correctly you need to clear a fixed point of reference and find the false reasoning.

 What is false reasoning?

See the answer and the analysis of
Where did the dollar go?Math brain teaser