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_64 (rank INTEGER, nation VARCHAR, silver VARCHAR)
### Question:
What was the average rank for south africa when they had more than 8 silver medals?
### Answer:
SELECT AVG(rank) FROM table_name_64 WHERE nation = "south africa" AND silver > 8