["Find total units: 8 + 5 = 13 units. Each unit = 260 / 13 = 20 books.","Novels = 8 x 20 = 160. Paperback:hardcover = 7:1 so hardcover novels = 1/8 x 160 = 20.","Textbooks = 5 x 20 = 100. Paperback:hardcover = 2:3 so hardcover textbooks = 3/5 x 100 = 60. Total hardcover = 20 + 60 = 80."]