Last month, Mr. Douglas sold 36 of his books. This month, however, he only sold 8 books. What was the percent change in book sales from last month to this month? A decrease of 77.77%
An increase of 3.5%
A decrease of 3.5%
An increase of 77.77%

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

These are the multiples of 15 but what you are probably asking or what are the factors of 15