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_54 (season_joined_league VARCHAR, seasons_at_this_level VARCHAR)
### Question:
What is the "season joined league" for the club that had 15 seasons at this level?
### Answer:
SELECT season_joined_league FROM table_name_54 WHERE seasons_at_this_level = "15 seasons"