Last week Fred had 29 dollars and Jason had 46 dollars. Fred washed cars over the weekend and now has 43 dollars. Jason delivered newspapers and now has 14 dollars. How much money did they earn by washing cars?
Fred had 29 dollars and Jason had 46 dollars. 

That means that together, they had 29 + 46 = 75 dollars. 

Fred washed cars over the weekend and now has 43 dollars. 

That means that he earned 43 - 29 = 14 dollars by washing cars. 

Jason delivered newspapers and now has 14 dollars. 

That means that he earned 14 - 46 = -32 dollars by delivering newspapers. 

Therefore, the answer is that they earned 14 dollars by washing cars.