So there are 14 books in total you want to do some simple math...
You are given that 8 of the books are new so the rest should be used and you need to figure out the used books so you need to subtract 8 used books from the total amount of books (14)
14-8 =6
So you can safely assume 6 books are used
Now a ratio is one to one so used books to new books
Used books : new books
6 : 8
Now if your told yo simplify then it’s just like simplifying a fraction to get
3 : 4
And now for used books to all books
Used books : all books
6 : 14
Simplified
3 : 7
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For any math help