To find the height of a stack of 8x10^9 books, we need to calculate the total thickness of all the books.
The thickness of one book is 3.1x10^-4 meters. So, the total thickness of 8x10^9 books can be calculated by multiplying the thickness of one book by the number of books:
3.1x10^-4 meters/book * 8x10^9 books = 24.8 meters
Therefore, the height of a stack of 8x10^9 books, each with a thickness of 3.1x10^-4 meters, would be 24.8 meters.
It's equivalent to about 81 ft.