The Browns traveled for a duel against the Texans.  The Texans scored first when Ka'imi Fairbairn kicked a 40-yard field goal to make it 3-0.  This would be followed up by the Browns tying the game up when Zane Gonzalez kicked a 41-yard field goal making the score 3-3.  Afterwards, the Texans would score 30 unanswered points:  Later on in the first quarter, DeShaun Watson found Will Fuller V on a 39-yard pass to make it 10-3.  In the second quarter, Johnathan Joseph returned an interception 82 yards for a touchdown to make it 17-3 followed up by Watson connecting with Braxton Miller on a 1-yard pass to make it 24-3 at halftime.  In the third quarter, a penalty got enforced on Kevin Hogan in the end zone giving the Texans a safety and increasing their lead to 26-3.  Watson then found DeAndre Hopkins on a 3-yard pass to make it 33-3.  The Browns scored twice in the fourth quarter when Jason McCourty returned an interception 56 yards for a touchdown to make it 33-10.  Finally, Hogan for Seth DeValve on a 3-yard pass to make the final score 33-17. The Texans routed the Browns, dropping them to 0-6 and handing them their 16th straight road loss.
Question: How many points did the Texans lead by at halftime?
Answer: 21