Question

cookies are sold singly or in packages of 3 or 9. With this packaging, how many ways can you buy 18 cookies?

Answer 1

i think plug and chug, because i don't see a snap way to do it
maybe we will see a patter
suppose there is one pack of 9
then how many ways?
9 9
9 3 3 3
9 3 3 1 1 1
9 3 1 1 1 1 1 1
9 1 1 1 1 1 1 1 1 1

Answer 2

i think that takes care of the number of ways if there is one 9
how about if there is not one 9?
then there are either
6, 5, 4, 3, 2, 1 or no packages of 3

Answer 3

i count 12
but it does not come with a guarantee