help wtih data sufficiency question clarification

Yes, it possible that there are books written in other languages. When we say 'not Spanish', it includes all other languages.
There are 80 books. 23 are in Spanish. How many are not in Spanish? 80 - 23 = 57 These 57 books could be in any language - English, French, German... All we know is that they are not in Spanish.
Acc to statement 1, 24 are fiction. Of these there are x books in Spanish and (x+6) books in all other languages (non Spanish). Each book will be either in Spanish or some other language (i.e. non Spanish)
so x + (x+6) = 24
Acc to statement 2, of the 23 books, y are fiction and (y + 5) are non-fiction. Each book will either be fiction or it will not be fiction (i.e. non fiction). There is nothing else possible. Non fiction means it is not fiction. Each book will either be fiction or it will not be fiction.
so y + (y+5) = 23