(2012 Buffalo Bills season)The game marked the anticipated return of former Texans number one draft pick Mario Williams, who had signed a multi-year $100 million contract with the Bills over the offseason, back to Reliant Stadium.  While Williams performed well in his return, the Bills were unable to muster up a touchdown drive over the Texans defense as Houston improved to 7-1 with a 21-9 win.  Also, the team took the all-time series to .500 with a 3-3 record against the Bills. Houston scored first on a 39-yard touchdown to make it 7-0. After 2 straight missed field goals by both teams, the Bills made one to cut it to 7-3. Buffalo got another field goal to make it 7-6 at the half. In the 3rd, Arian Foster scored to make it 14-6. Late in the 3rd, Buffalo made another field goal to make it 14-9. Schuab found Garrett Graham to make the final score 21-9. Houston improve to 7-1
Question: How many points did the Texans manage to win by?
Answer: 12