To answer this question, you will need to find the greatest common factor of all the numbers of flowers. This will be the biggest way we can divide them all out evenly.
There are 2 ways you can find the gcf:
1. List all factors
72-1,2,3,4,6,8,9,12,24, 36, 72
80-1,2,4,5,8,10,16,20,40,80
68-1,2,4,17, 34, 68
The greatest common factor is 4.
2. List prime factorization and match all prime numbers from all 3 lists.
72=2x2x2x3x3
80=2x2x2x2x5
68=2x2x17
2x2=4 flower arrangements
Each of the 4 center pieces will have 18 carnations, 20 lilies, and 17 rosebuds.