Problema Solution

The amount of a school lunch and the amount of money owed are in a proportional linear relationship. I had to borrow money from the cafeteria 5 times and I owe them $17.50.

Answer provided by our tutors

Each time money was borrowed the same amount... or the statement is ambiguous enough that other interpretations could be intended.  We assume that the relationship is not increasing. 

17.50/5

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3.5

So $3.50 was borrowed from the school lunch each day.