Withey grabbed 11 rebounds and Ben McLemore scored 13 points for the Jayhawks (21-4, 9-3 Big 12), who won their second straight game and moved into a tie with Kansas State and Oklahoma State atop the Big 12 standings.
Elijah Johnson chipped in with 12 points for Kansas, which never trailed in the contest.
Myck Kabongo paced the Longhorns (11-14, 3-9) with 13 points.
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