Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_15 (high_rebounds VARCHAR, location_attendance VARCHAR, date VARCHAR)
### Question:
What is High Rebounds, when Location Attendance is "Madison Square Garden Unknown", and when Date is "May 18"?
### Answer:
SELECT high_rebounds FROM table_name_15 WHERE location_attendance = "madison square garden unknown" AND date = "may 18"