Algebra II help? Thanks :)?

Can someone help me set up the two equations I would use for this problem?
Marcela went to the store and paid $6.50 for 2 gallons of milk and 1 loaf of bread. The following week the prices were the same and her bill was $7.75 for 1 gallon of milk and 3 loaves of bread.What is the cost of a loaf of bread?
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