What is the guess and check method

The box plots show the average speeds, in miles per hour, for the race cars in two different races. which correctly describes the consistency of the speeds of the cars in the two races?

If 3 3/4 lb. of candy costs 20.25 how much would 1lb. of candy cost

Alex measured the length of an item to be 3.7 cm. the actual length is 3.5 cm. what is alex’s percent error?