One thing I don't get in the explanation is when it says the distance from A-D is 3 times the distance between C to D...then they multiply that distance by 6?? It's probably a stupid question but for some reason I'm not getting why to multiply by 6 instead of 3...
You are right we will multiply the distance between C&D by 3 to get the distance between A&D.
I think the 6 in "6(5^13-5^12)" is a typo in the solution. They correct that in the subsequent calculation when they state: 5^13 - 3
(5^13 - 5^12). And the final OA is correct.
The three most significant times in your life are:
1. When you fall in love
2. The birth of your first child
3. When you prepare for your GMAT