Complex sentence: After she retired from the Metropolitan Opera, Rankin devoted herself to teaching, first at the Academy of Vocal Arts in Philadelphia, from 1977 to 1984, and then privately in New York City until she retired in 1991.
Split into simpler sentences: After she retired from the Metropolitan Opera, Rankin devoted herself to teaching, first at the Academy of Vocal Arts in Philadelphia, from 1977 to 1984. She taught privately in New York City until she retired in 1991.