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_30 (year_began_making_autos INTEGER, year_joined_gm VARCHAR)
### Question:
What is the average year to begin making autos for a brand that joined GM in 1917?
### Answer:
SELECT AVG(year_began_making_autos) FROM table_name_30 WHERE year_joined_gm = 1917