Answer:
5:9
Explanation:
20÷4=5
36÷4=9
If you divide 20 by 4 you get 5. If you divide 36 by 4 you get 9. You need to be able to divide each number in the ratio by the same number. In this case, that number is 4. You can tell that this ratio (5:9) is in simplest form because 5 is a prime number and cannot be simplified any more.
If you want to check this divide the ratio by 2 two times. Or just divide it by 4 once.
20÷2=10 → 10÷2=5
36÷2=18 → 18÷2=9