CREATE TABLE table_name_56 (goal_difference VARCHAR, points_1 VARCHAR, goals_against VARCHAR)

When the Points 1 was 51 and the Goals Against was less than 66, what was the Goal Difference?
SELECT goal_difference FROM table_name_56 WHERE points_1 = "51" AND goals_against < 66
SELECT "goal_difference" FROM "table_name_56" WHERE "51" = "points_1" AND "goals_against" < 66