The trick to this question is here…
This meant, that the 3 men each paid $9 for the room, which is a total of $27. Add in the $2 that the bellboy kept = $29.
the word “add” is what throws people…you actually have to subract. the men paid $27…subract the $2 the bellboy has and you get $25 paid to the desk.
and here is a simple way of understanding…
"Let’s give each of the $30 a number from 1-30, keep track of each individual dollar, and see how the problem works.
Dollars numbered 1-30 are given to the manager. Then he wants to give $5 back, so he keeps the dollars numbered 1-25, and gives numbers 26-30 to the bellboy in the form of a five 1 dollar bills. numbers 26, 27, 28, 29 and 30. He gives numbers 26, 27 and 28 to the customers and keeps numbers 29 and 30 for himself."