CREATE TABLE table_name_15 (high_rebounds VARCHAR, location_attendance VARCHAR, date VARCHAR)

What is High Rebounds, when Location Attendance is 'Madison Square Garden Unknown', and when Date is 'May 18'?
SELECT high_rebounds FROM table_name_15 WHERE location_attendance = "madison square garden unknown" AND date = "may 18"
SELECT "high_rebounds" FROM "table_name_15" WHERE "date" = "may 18" AND "location_attendance" = "madison square garden unknown"