CREATE TABLE table_203_174 (id DECIMAL, "rank" DECIMAL, "film" TEXT, "year" DECIMAL, "opening weekend\ ( three day ) " TEXT, "inflation-adjusted\ ( 2014 usd ) " TEXT)

what is the average opening weekend gross between iron man 3 and the dark knight ?
SELECT AVG("opening weekend\n(three day)") FROM table_203_174 WHERE "film" IN ('iron man 3', 'the dark knight')
SELECT AVG("opening weekend\n(three day)") FROM "table_203_174" WHERE "film" IN ('iron man 3', 'the dark knight')