Answer:
Number of books =10
Total number of ways =10!
Given pair of books to be together considering them as one
total sets =9
Number of ways of arranging them =9!ways
Those two books can be arranged in 2!
Total ways that the pair of books is together
⇒9×2
Number of ways that are not together
⇒10−9×2
⇒9(10−2)
⇒8×9
