Answer:
89 pages
Step-by-step explanation:
If a page in the album can hold 9 coins, then for 900 total coins, there are 100 pages in the album or [tex]\frac{900}{9}[/tex].
If the problem informs that 11% of the pages are empty then that means that 11% of the 100 pages are empty or 11 pages.
Since the problem asks for the number of filled pages, the total number of pages in the album is subtracted by the number of empty ones or 100 - 11 = 89.