DURHAM, N.C. — Mike Krzyzewski tore off his jacket, he slapped the floor, he gestured toward the crowd — anything to spark his emotionally spent Duke players. And then his lone scholarship senior got rolling and saved the fourth-ranked Blue Devils. Quinn Cook scored all 17 of his points in the second half, and Duke beat Georgia Tech 72-66 on Wednesday night to give Krzyzewski his Atlantic Coast Conference-record 423rd league victory.