Brett cannot spend more than $30, so the cost of the books and the shipping charge have to be less or equal to $30, we can express this as in an inequality, like this:
Where n is the number of books purchased, since each book costs $4, 4 times n equals the total cost of the books and 2 is the shipping charge. We can solve for n in the inequality like this:
Then, brett can afford no more than 7 books.