There is no extra dollar.
The three men paid $30 for a room.
The manager realized that the room only
ought to have cost them $25, so he sent
the bellhop back with $5 to be returned
to them.
Out of the original $30, here's where
it all went:
Kept by motel: $25
Stolen by bellhop: 2
Returned to men: 3
---
Total: $30
===
Another way of looking at it: The
three men ended up paying a total of
$9×3=$27. That's $25 for the room
plus the $2 stolen by the bellhop.
The question tries to trick you into
adding the $2 stolen by the bellhop to
the total of $27 that the three men end
up paying, for a total of $29, and then
wondering why it doesn't add up to the
original $30. But this is nonsense, as
the $27 already includes the stolen $2
($25 for the room plus the stolen $2
equals $27).
The $27 that the men ultimately end up
paying, plus the $3 that was returned
to them, adds up to the original $30. The
$25 that the men were supposed to pay
for the room, plus the $5 that the bellhop
was supposed to return to them, equals the
original $30.