What is the length of the hypotenuse?

please help!

Hi my sisters and brothers can tell me the answer because i don’t understand the 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

2. explain in words how you plot the point (4, −2) in a rectangular coordinate system.