Setting it up Determine the cost per book Let x represent the number of books she purchased. The cost per book will be
Setting it up She gives 15 to her brother and sells the rest for $330 Her revenue per book will be 330 x-15
Equation Revenue - Cost = Profit R(x) - C(x) = P(x) 330/x /x = 1.5 Solve for x to determine the number of comic books in the box. Substitute this answer into the cost expression to get the original price of each book.