Answer: If he has 3 mystery books, and those are 1/8 of his whole collection, he has 24 books.
Step-by-step explanation:
3 = 1/8 × x
multiply both sides by the reciprocal of 1/8 which is 8/1 ("flipped fraction")
8 × 3 = 8/1(1/8) x When you multiply a fraction by its reciprocal, it produces 1, so it "cancels" in the multiplication
24 = x
This may seem complicated, but understanding the process will help you solve more complicated questions like this in the future, I hope.