For the benefit of those who find the above to be alien hieroglyphics,
Primary School maths
question that 99 out of 100 uni students answer wrongly.
A young man wants to buy a gift at Mr. Wang's shop.
The item's cost price is $18, while the selling price is $21.
The young man pays with a $100 bill, but Mr. Wang has no change.
Mr. Wang then goes to a nearby shop to change $100 of small notes, and returns the young man $79.
Subsequently, the nearby shop finds the $100 to be counterfeit, so Mr. Wang has to return the shop $100.
* How much did Mr Wang lose?