Suppose you write a book. The printer charges $4 per book to print it, and you spend 5500 on adverti

Suppose you write a book. The printer charges $4 per book to print it, and you spend 5500 on advertising. You sell the book for $15 a copy. How many copies must you sell to break even.

Profit per book is:
P = 15 - 4
P = 11

We want to know the number of books (b) such that:
11b = 5500 <-- Breakeven means cost equals revenue

Typing this equation into the search engine, we get:
b = 500