Answer:
first of all there are many ways to compare numbers. example
- the digit they have
- the pattern they have
- there amount
I don't know how to compare them but I try my best
Explanation:
the first 3 numbers have only one digit but the 4th has 2 digits.but it in my opinion you don't want this answer.
so this is not the reason
3 have 2 factor
6 have 4 factor
9 have 3 factor
12 have 5 factors
so as the number increase the factors should increase but 9 has less factors than 6 .so I think 9 is the different one