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