C. 36 books - non-fiction = 12, fiction = 24, hardcover = 9, paperback = 27
Initial equation -> 2/3f + 1/3nf = 1/4hc + 3/4pb
smallest common denominator is 12
Multiply by 12 -> 8f + 4nf = 3hc + 9pb doesn't match because 4nf < 10
Next common denominator = 24 -> 16f+8nf = 6hc+18pb doesn't...