It A because each book that he is buying cost 2.5 and the amount of books he buying is unknown so the variable x is place right next to 2.5. But if he wants to buy lunch he has to subtract 8 dollars from his total amount. So since David has a limit of $50 the symbol for the equation should be the less than symbol< because he has to be able to buy lunch and buy the book with less than 50 dollars.
