Can someone pls sub to meh yt ch annel ill sub to u in return

I've never been good at math he told he loves but he keeps cheating on me, so it ain't adding up sis

What is the missing step in this proof ?

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