ok here it goes i will try and explain it properly:
three guys walk into a hotel and ask for one room with three beds.
once they unpack they decide to go downstairs and pay for the night, so they ask the receptionist how much it would cost.
she replies that will be thirty pound please, so as there is 3 men they decide to pay £10 each.
unfortunately the lady makes a mistake as she finds out it is only £25 for the room altogether.
she decides that since they cant split the £5 between them she will give them £1 each and take £2 herself.
so that means the men only pay £9 per room instead of the £10
If we add this up:
Receptionists £2
Man 1 £9
man 2 £9
Man 3 £9
9+9+9+2 = 29. (Y)
where did the other pound go?