[K.S.H]

They didn't pay £9 they paid £10 (£30) and had £5 refunded, I know what your getting at and it doesn't work out, it "appears" that theres £1 missing, we got told the right way to work it out was the way cazzer posted.
Another way of putting it is, they paid £30 to hotel, hotel refunded £5, blokes got £3 each = £27 paid, problem is when you add the £2 that was pocketed, it's being added instead of being taken away