Sure, the common difference is -3, but like you have to multiple it and stuff, so it goes like this: -2,6,-18,54,-162,486,-1458,4374,-13122,39366,-118,098,354294.
So then, add all of the 12 terms I stated, and that will equal to 265,720
Therefore, the sum of the first 12 terms of that geometric sequence is 265,720.
