CREATE TABLE "isc_tracks" (
  "track_name" text,
  "location" text,
  "length" text,
  "seating" real,
  "year_opened" real,
  "year_acquired_a" real
);

Question: What is the year opened for Chicagoland Speedway with a seating smaller than 75,000?
SQL: SELECT AVG("year_opened") FROM "isc_tracks" WHERE "track_name"='chicagoland speedway' AND "seating"<'75,000';