Jerson is selling fruit at the Farmers' Market. To attract customers to his booth, he has made up a contest! He has these photos of combinations of fruit on display. His contest is to find out how much each fruit weighs.
8.25 lbs.

9.5 lbs.

11.5 lbs.

Note: Assume that both of the melons weigh the same, both of the pineapples weigh the same, and both of the limes weigh the same.
Melanie looks at his photos and tells him, "I know how much one melon weighs."
How might Melanie have figured out how much one melon weighs? How much does each type of fruit weigh?