if Caroline buys 4 NF books and 7F books, there's 11 books altogether. 4 out of 11 books is 36% or 0.3636363636... I marcus buys 6 NF books and he buys 3F books, there's 9 books altogether and 33% of the books will be fiction. therefore, he needs to buy less than or exactly 3 fiction books.