Last week Fred had 37 dollars and Jason had 19 dollars. Over the weekend Fred delivered newspapers earning 20 dollars and washed cars earning 27 dollars. How much money did Fred earn over the weekend?
Fred had 37 dollars last week. 
He earned 20 dollars from delivering newspapers. 
He earned 27 dollars from washing cars. 

Adding those three numbers together, we get that Fred earned 84 dollars over the weekend.