SELECT "Winning score" FROM table_17939 WHERE "Championship" = 'PGA Championship (3)'
What was the winning score of the PGA Championship (3)?
CREATE TABLE table_17939 (
    "Year" text,
    "Championship" text,
    "54 holes" text,
    "Winning score" text,
    "Margin" text,
    "Runner(s)-up" text
)