15
4
12
9
Answer is Right!
Answer is Wrong!
The missing number is 9.
The numbers in the sequence are all multiples of 3, except for 12. This is because 12 is the sum of the first two numbers in the sequence, 3 and 9. Therefore, the missing number must be a multiple of 3 that is not 12. The only number that fits this description is 9.