Puzzle 114 - solution

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 This puzzle is quite simple.

Let us say John has worked for x days. Which means he earns x dollars each day. So total money he gets is x2 

Robert earns one dollar more. Robert earns x+1 dollar per day. He worked one day less. The number of days he has worked is x-1. 

Robert earns (x+1)(x-1) =  x2 -1 dollars

John earns more.  

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