Question 550962
This problem is asking for the least common multiple of 12 and 9

I like to solve lcm problems by primes

12's prime factorization is 3*2*2

9's prime factorization is 3*3

This will give me 3*3*2*2 as the lcm
which would be 36

Another way of doing this is just saying 

12,24,36
9,18,27,36

So we will need 36 bags (and 3 boxes of toothbrushes and four boxes of dental floss)