Answer:
297 pages
Explanation:
Number of pages of longest book = 396 pages
Now we are given that her shortest book has one-fourth as many pages as the longest.
Number of pages of shortest book =
=
=
Now we are given that the book in the middle of her shelf has three times the number of pages of the shortest book.
So, Number of pages in middle book:
=
=
=
Hence the middle book have 297 pages.