This is a bit confusing for me, can anyone help me out?

If a baby uses 15 diapers in 2 days, how many diapers will the baby use in a year?

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

Plot a point at the y-intercept of the following function on the provided graph. 3y=-5x+7 20 points