Answer:4:5
Explanation:
If you divide both by two, you get 8 pink stripes and 10 green stripes.
Then, if you divide those by two, you get 4 pink stripes and 5 green stripes and since that can't be simplified anymore, that is your answer:
4 pink stripes: 5 green stripes
One way that you can check it is by making sure that in the beginning, there are less pink stripes than green stripes so make sure that in the end, there are still less pink stripes than green stripes.