Do multiplication first.

3 x 3 = 9.

Now we rearrange the problem to look like 3 + 9 - 3 + 3. Addition and Subtraction are meant to be performed in that order, but in this case it really doesn't matter. The answer ends up being 12.

If we ignore the order of operations, as is acceptable since there is no real requirement to follow this rule, we get a different answer.

3 + 3 = 6.

6 x 3 = 18.

18 - 3 = 15.

15 + 3 = 18.

So technically, the answer could also be 18.

Do I agree with this? No. But again, the order of operations isn't really a "rule" in mathematics.