Pythag = Pythagorean record, which is calculated from Runs Scored and Runs Allowed. In other words, expected W/L. Basically a more luck neutral winning percentage. I figure everyone's heard of that, too.
As far as the math goes, the rest is just basic arithmetic.
The reason I said 2*Wilson + Pujols - Darvish is because we're comparing the Angels and Rangers, so Wilson is both added to the Angels and subtracted from the Rangers.
The only other thing I can see in there that might be confusing is FAN. That's just one of the projection systems Fangraphs uses (and the only one that was readily available with WAR totals, which is why I used it). The way they calculate it is by doing a (possibly weighted?) average of reader projections for players for the coming year.
It wasn't that bad, guys, come on. And as for whether it's necessary... if you want to answer the question, you've gotta use the data! You said you thought Wilson + Pujols + return of Morales made up a 10 game difference. My initial inclination was to think that that would at least not more then make up the gap between the Angels & Rangers (and thus make the Angels clear favorites), but I figured it made more sense to actually run the numbers then to just say it.