Can someone help? I hate math so much lol I don’t understand

Do more practice. After more practice you can understand math.

9!=362880 ways

Step-by-step explanation:

It is given that there are 4 different mathematics books and 5 different science books.

So basically there are 9 different books. So we have 9 choices for the first book, 8 choices for the second book, since we have placed the first one. We have 7 choices for the third book and so on. Therefore, we can arrange 9 different books in,

!9 ways, on solving !9 we get,

So there are 362,880 ways to arrange 9 different books if there are no restrictions.