Divide everything by 10 and you get: one pound of tomatoes and 5 pounds of bananas cost $3.50. But we haven't any more information to decide how much of the money pays for the tomatoes and the bananas separately. For example, if the tomatoes are $1 for a pound, then 5 pounds of bananas cost $2.50, and bananas are 50 cents a pound. If tomatoes are 50 cents a pound, then 5 pounds of bananas cost $3, so bananas are 60 cents a pound.