Which City of license has a Frequency MHz of 91.5 fm?
CREATE TABLE "repeaters" (
  "call_sign" text,
  "frequency_m_hz" text,
  "city_of_license" text,
  "erp_w" real,
  "fcc_info" text
);
SELECT "city_of_license" FROM "repeaters" WHERE "frequency_m_hz"='91.5 fm';