It's pretty easy to figure out. We have a 2-game lead with 7 to play and even if we lose today, we'll still own the tiebreaker, so yes, the magic number is 5: Any combination of M's wins and Stros losses that adds up to 5 and we win the AL West.
The other thing to keep an eye on is the first round bye. The Blue Jays have all but clinched one of the byes, but the other one is up for grabs. We win today, and the focus will turn to how the Tigers are doing. Detroit has 3 games remaining against Cleveland, who are as hot as a firecracker.