As her senior project, Julie has decided to raise money for a charity by hosting a Spaghetti Dinner. In order to have the dinner, she had to borrow $100 to rent the hall from her parents (which they expect to get back.) She is going to make $6 for every dinner purchased. Write an algebraic expression to describe the amount of money Julie will raise for any number of dinners purchased. Describe what the variable represents in this situation.