Sabah has $450 to pay for college textbooks. she expects to pay about $75 per book. her friend told her that 4 of them can be checked out of the library for free. complete the equation below to find the total number of books that sabah can get for her classes. use b to represent the total books. the equation has to look like this format: =? you can use any of these numbers to fill in the equation: 4, 10, 75, 300, 450, b