How many different ways are there to arrange 12 books on shelf

6 ways

You can arrange the 9 normal books in 9 ways, creating 10 slots where one of the three common books may be placed.

Step-by-step explanation:

There are 10⋅9⋅8 ways to choose different slots for those three books. The total number of allowable arrangements therefore is 9!⋅720=261273600