Complex sentence: At 15 years of age she won three gold medals at the 1972 Olympic Games; in the 100m backstroke Belote defeated her American teammate and record holder Susan Atwood.
Split into simpler sentences: At 15 years of age, she won three gold medals at the 1972 Olympic Games. In the 100-meter backstroke, Belote defeated her American teammate and record holder Susan Atwood.