Houston has been eliminated from first place.

To show that Houston is eliminated from first place, we start with the current standings:
            Team	W	L	GL	PCT	GB
         Seattle	91	71	0	0.562	0.0
         Houston	87	75	0	0.537	4.0
           Texas	81	81	0	0.500	10.0
         Oakland	76	86	0	0.469	15.0
     Los Angeles	72	90	0	0.444	19.0
           Total	407	403	0

Houston can finish the season with at most 87 + 0 = 87 wins and will finish the season behind the following teams:
Seattle has already won 91 games.
# Houston Astros' magic number
# Houston's magic number
# Astros' magic number
# MLB Playoff Race