You know 15 odd number so first you will need time 2 1/2 by 7 and you know that make 14 dozens cookie so you need 17 1/2 cups of floor and you 2 1/2 is 2 dozens so divide by 2 you get 1 dozens so it 1 1/4
17 1/2 + 1 1/4 = 18 3/4
Total of 18 3/4 of cup of flours to make 15 dozens of cookie