Complex sentence: During the 2011--12 season, Takahashi/Tran placed fourth at their first Grand Prix assignment, the 2011 Skate Canada International, and then won the silver medal at their second event, 2011 NHK Trophy.
Split into simpler sentences: During the 2011--2012 season, Takahashi/Tran's first Grand Prix assignment was 2011 Skate Canada International, where they finished fourth. They won the silver medal at their second event, 2011 NHK Trophy.