That is, as soon as I paid 30 yuan, I found 1 yuan.

3 X 9 = 27 yuan+2 yuan hidden by the waiter =29 yuan 29+ 65438+ 0 pieces returned now =30.

This is a magical topic. If you think according to his ideas, you will only feel confused, but if you touch your own ideas a little, you will find the mystery. First of all, the 9 yuan money spent by each person already includes the 2 yuan hidden by the waiter (that is, the preferential price of 25 yuan+the waiter's possession of 2 yuan =27 yuan =3*9 yuan). Therefore, when calculating the composition of 30 yuan, the 2 yuan money hidden by the waiter cannot be counted, but should be added with 1 yuan returned to everyone. Namely: 3*9+3* 1=30 yuan is just right!