Scale factors and it so hard i dont no what to do

What is the value of x in the this question ?

Suppose you are an avid reader and are looking to save money on the cost of books instead of paying about $20 for each book, you decide to look into purchasing a kindle for $120 you can purchase e-books for about $5 each 1. find the slope-intercept equation for the cost of the hard copy of books using x to represent the number of books 2. find the slope-intercept equation for the cost of the kindle with cost of e-books using x to represent the number of books

8. kelly wants to buy a magazine that is $25. later the magazine was marked up an additional 20%. what is the new price?