Can tu solve this?

That would depend on how much volume can the bag contain and how much mass it can hold.

what books?? when i have my brain =D

Depends on how big the bag is -.-

26 - how do i know. I tried.

tu didn't specify the size of bag/books, type etc so i assumed it was for us to try.
I tried, and the answer is 26.

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21?

no wait, none cause it wouldn't be empty!

empty O____________O bag.....idk

NONE! ITS A EMPTY BAG!

13

Once tu put a book into a empty bag, it is no longer empty.
If you're asking how many libros would fit into an empty bag, that depends on the size of libros and the bag. :)

no idea it all depends how big the bag is so probly at least 10-20 books

1. Because once tu put one book in, you're not putting any más libros into an EMPTY bag, it already has a book in it.

I read "the contest is done the answer is ONE BOOK BECAUSE IT WON'T BE EMPTY AFTER THIS" in the comentarios and I am going to disagree, tu can fit 2, 3, 4, o more, just as long as tu put them all in at the same time.