the sequence is: 3 , 12 , 30 , 66
12-3 = 9
30-12 = 18
66-30 = 36
18/9 = 2
36/18 = 2
Because the difference of 2 of the numbers divided by the difference of the other 2 numbers is equal to 2, on of the steps is multiplying the previous number by 2,
But since the previous number multiplied by 2 does not equal the next number, the other step needed is to add 3 first.
The answer is 4) add 3, multiply by 2
