CREATE TABLE table_55013 ("Date" TEXT, "Score" TEXT, "Set 1" TEXT, "Set 2" TEXT, "Set 3" TEXT, "Total" TEXT)

What is the score for set 2 when set 3 was 15 6?
SELECT "Set 2" FROM table_55013 WHERE "Set 3" = '15–6'
SELECT "Set 2" FROM "table_55013" WHERE "Set 3" = '15–6'