CREATE TABLE table_name_7 (date VARCHAR, result VARCHAR, site VARCHAR, attendance VARCHAR)

What is the Date at memorial stadium minneapolis, mn with an Attendance of 20,000, and a Result of w52-0?
SELECT date FROM table_name_7 WHERE site = "memorial stadium • minneapolis, mn" AND attendance = "20,000" AND result = "w52-0"
SELECT "date" FROM "table_name_7" WHERE "20,000" = "attendance" AND "memorial stadium • minneapolis, mn" = "site" AND "result" = "w52-0"