the answer is 6 1/8 pizzas. 35x8 is 280 slices in total to sell. 13x8 is 104 plus 1/8 (which equals to 1 slice) is 105. 15x8 is 120 plus 3/4 (which equals to 6 slices) is 126. Add 105 and 126 to get 231 slices. Subtract 280-231 to get 49 and divide that by 1/8. That equals to 6.1 or 6 1/8 pizzas.