Troy has an album that holds 400 compact discs, and each page holds 4 compact discs. If 66% of the album is empty, that means that 34% of the album is filled with compact discs. Since each page holds 4 compact discs, that means that 34% of 400 compact discs is 136 compact discs. Since each page holds 4 compact discs, that means that 136 compact discs is 34 pages. Therefore, 34 pages are filled with compact discs.