+870 
These questions aren't really hard, but there is a trick in them. That's all I can tell you !
1) 48/2(9 + 3) = 24(9 + 3) = 24*9 + 3*9 = 216 + 27 = 243
2) 8 - 1*0 + 2/2 = 8 - 0 + 1 = 9
3) 12 - 1*0 + 4/2 = 12 - 0 + 2 = 14
+870 Anonymous (the first one), even though your first answer is wrong (the beginning was right, then it got kinda ugly), I think you deserve a brownie (Sorry, all my cookies are gone, but I think brownies taste good as well) for the two other ones, and around 13.5/20 (Sorry, I cannot put thirds of points but only halves, so I round the the next half point above).
As for you Cphill, the first answer is actually 288. So you also deserve a brownie for your answer (but no mark since you gave only one answer) :
MaiaMitchell and Anonymous (the second one), you were right when you told me that "Anonymous 1"'s 1st answer was right, anyway, you didn't gave me any answer. But that's OK, you might deserve each a sweet fot your remark.
Anonymous, (the third one), I am sure that it isn't 2 since I checked the answer with 3 calculators (including Google calculator):
They all answered 288, never 243, let alone 2. Check it if you have any doubts.
