Complex sentence: In 1990, Six Flags Great Adventure had 5 roller coasters, but due to ride rotation programs and the purchase of Batman the Ride, the park was down to only three by the end of 1992.
Split into simpler sentences: In 1990, Six Flags Great Adventure had 5 roller coasters. But due to ride rotation programs and the purchase of Batman the Ride, the park was down to only three by the end of 1992.