Complex sentence: The 1979-80 Philadelphia Flyers season was the 13th season of Philadelphia Flyers NHL ice hockey in Philadelphia, Pennsylvania and saw the Flyers go undefeated a record 35 games and reach the Stanley Cup Finals.
Split into simpler sentences: The 1979-80 Philadelphia Flyers season was the Philadelphia Flyers 13th season in the NHL. The Flyers went undefeated a record 35 games and reached the Stanley Cup Finals.