Duke’s Cooper Flagg reacts after hitting a 3-point shot during the first half against George Mason in Durham, N.C., on Tuesday night. Ben McKeown/Associated Press

DURHAM, N.C.  — Freshman star Cooper Flagg of Newport, Maine,  had 24 points and nine rebounds as No. 5 Duke held George Mason to just 29.4% shooting in a 68-47 win Tuesday night.

Flagg, a preseason Associated Press All-American, shot 7 for 20 from the field but was active on the glass. He had four assists and was perfect in eight trips to the foul line for the Blue Devils (9-2).

Jalen Haynes scored 18 points to lead the Patriots (7-4), but only one teammate hit more than two shots.

TAKEAWAYS

George Mason: The Patriots had won five straight since a double-overtime loss at East Carolina on Nov. 16. George Mason fell to 4-25 against current ACC teams.

Duke: The Blue Devils returned to the court after a week off for exams following a win against Incarnate Word.

KEY MOMENT

In a game with few stretches of flowing offense, Duke’s 9-0 burst early in the second half stood out in expanding a 27-18 lead. Flagg hit two free throws and a jumper, then got in the lane for a score before whipping a pass to Tyrese Proctor for a corner 3-pointer to make it 36-18 at the 16:40 mark.

George Mason briefly got within a dozen midway through the second half but no closer.

KEY STAT

This promised to be a defense-oriented matchup, with George Mason ranked No. 3 nationally in field-goal percentage defense (.354) and Duke fifth (.362). The teams combined to make 15 of 61 shots (24.6%) in the first half, but the Blue Devils made 12 of 23 (52.2%) after the break while the Patriots warmed up to a tepid 35% (14 of 40) in the final 20 minutes.