Complex sentence: Westmount is an affluent on-island suburb on the Island of Montreal, an enclave of the city of Montreal, in southwestern Quebec, Canada, with a population of 19,931 as of the Canada 2011 Census.
Split into simpler sentences: Westmount is an affluent on-island suburb on the Island of Montreal. It is an enclave of the city of Montreal, in southwestern Quebec, Canada, with a population of 19,931 as of the Canada 2011 Census.