Still not getting the logic on this problem. Can someone please explain? I don't think any of the posts in the forums have tackled this one.

Hi all, I took my GMAT this week and scored a 750 (Q50,V40). I wanted to share my experience and some tips as payback, since I found the the MGMAT blogs and forums very helpful... When I started my preparation I did not get the MGMAT guides. After a few weeks of studying in my first practice test I...