Three men eat a meal at a restaurant. The bill is �30 [it's an old story], so they pay �10 each. After they leave, the managerrealises ha has made a mistake and the bill should have been �25. He gives one of his employees �5 to return to the men. The employee thinks, "�5 can't be shared equally between three people, so I'll give them back �3 and keep �2 for myself." Now the men have paid �9 each, making �27, and the employee has kept �2. This makes �29. where is the missing pound.
It is, of course, complete nonsense. The men have paid �27, the manger has �25, and the employee has �2. There is no reason to add the �27 and the �2.