They paid $30, but the owner returned $5, which means the cost is only $25. The bellhop knows this, so he take $2 of the $5 leaving $1 to be return to each person. That means that they each paid $9 making it a total of $27, more than the cost of the room. You don't need to add $2 to the $27, because that wasn't the cost of the room. The cost was only $25, so +$5 =30. So no money is actually missing, they just added incorrectly.