Complex sentence: The Western Hockey League used best-of-nine playoff series for the Western Division playoffs from the 1983-84 season through the 1990-91 season because of the unequal division alignment of the league at this time.
Split into simpler sentences: The Western Hockey League used best-of-nine playoff series for the Western Division playoffs from the 1983-84 season through the 1990-91 season. Because of the unequal division alignment of the league at this time.