Where is the money?

Three people went to stay for $30 a night. The three people paid 10 yuan each to make up $30 and gave it to the boss. Later, the boss said that only $25 would be enough for the discount today, and $5 was ordered to return the waiter to them. The waiter secretly hid $2 , and then distributed the remaining $3 to the three people, each of whom was divided into $1 . In this way, each person paid $10 at the beginning, and now returns $1 , That is 10-1 = 9, each person only spent $9 , 3 people $9 per person, 3 X 9 = $27 + $2 hidden by the waiter = $29, where did the $1 go? ? ? ? ?