Restaurant Puzzler answer...

The answer is that the figures will not add to £30 because they are not from the same equation. Equation 1: What's been paid is £25 for the meal - which is in the till, and £2 for the tip - in the waiter's pocket, leaving the men with £1 each, ie £3, which all adds up to £30. Equation 2: The men have each paid £9 for the meal and the tip together, ie £27, and they each have a £1 in their pocket, ie £3, which all adds up to £30.