OG 13th DS #41

[minkang521]

[deleted because problem is from a banned source - see below]

I figured out that up top, x+y = 15 by doing algebra. With this constraint, wouldnt both 1 and 2 be sufficient? I dont get why both need to be used (answer c).

I thought that the point of the two facts are so that we could compare to the constraint given in the question stem.

For fact 1), wouldnt you look at it like x, y that satisfies both equations? x+y=15 and x-y=9? In which case, the answer would be D, no?

Please help!

[tim]

OG is a banned source; it is illegal to post OG questions anywhere on the web. If you are in one of our classes, please ask OG questions during office hours or before/after class..

as for this question, you haven't done anything to demonstrate that 1 or 2 by itself would tell us whether x+y=15..