Complex sentence: He was 12th at the 2011 and 2012 U.S. Championships, 15th in 2013,11th in 2014, and 9th in 2015.
Split into simpler sentences: He was 12th at the 2011 and 2012 U.S. Championships. He placed 15th at the 2013 U.S. Championships, 11th in 2014, and 9th in 2015.