CREATE TABLE table_22347090_6 (no_in_series INT, production_code VARCHAR)

What episode number in the series had a production code of 3x7554?
SELECT MIN(no_in_series) FROM table_22347090_6 WHERE production_code = "3X7554"
SELECT MIN("no_in_series") FROM "table_22347090_6" WHERE "3X7554" = "production_code"