Pleaseee help i will mark this is my final exam help

The graph shown is the graph of which function?

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

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