The printer charges $4 per book to print it, and you spent $3500 on advertising. you sell the book for $15 a copy. how many copies must you sell so that your income from sales is greater than your total cost?

15x > 4x + 3,500 ($15 per copy must exceed $4 per copy of a printer and an initial amount of $3,500 from advertising)
11x > 3,500 (Simplify, subtract 4x from both sides)
x > 318 2/11 (Divide both sides by 11)
You cannot sell part of a book, so you round to the higher whole number.
You must sell at least 319 books.

If you need an equation, it would be y=2x+8, y would be how long it grew, x being weeks.if you need how long he was asleep, it would be 4 weeks if he started with no beard, the equation would be x=8÷2if he did have a beard before hand, the equation would be 2w+x=8