Brayden has 4 textbooks. If you think of this as positions on the shelf:
- Brayden has 4 options for the first position.
- Once he's placed the first book, he has 3 options left for the second position.
- Once he's placed the second book, he has 2 options left for the third position.
- Once he's placed the third book, he has 1 option left for the fourth position.
In total he has 4·3·2·1 ways, or 24 ways, that he can set up the books on his shelf.
