The Titans forced four Jets turnovers; Jake Locker threw three touchdowns off turnovers as the Titans led 24-6 at the half.  Locker was knocked out of the game in the third quarter following hits from Muhammad Wilkerson and Quinton Coples, suffering a right hip injury; a subsequent MRI showed no major damage to Locker's hip and he was sidelined for the next two games.  Ryan Fitzpatrick finished the game, throwing a 77-yard score to Nate Washington.  Geno Smith of the Jets was intercepted twice, but the most-popularized play came when he fumbled behind his back at the Titans goalline and Karl Klug fell on the touchdown.  Tennessee won 38-13.
Question: How many points were the Titans leading by at halftime?
Answer: 18