Answer:
12
Explanation:
By analyzing the terms in your set, we can see that each integer is increasing by three.
Following this pattern, our answer should be 9 + 3, because 9 is the most recent and closest term in the sequence.
-3, 0, 3, 6, 9, 12 is our completed sequence. Of course, it will keep on going for infinity.
But you asked for the next term, so the answer is 12.