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_24850630_3 (venue VARCHAR, race VARCHAR)
### Question:
The MacKinnon Stakes races took place on how many venues?
### Answer:
SELECT COUNT(venue) FROM table_24850630_3 WHERE race = "Mackinnon Stakes"