Complex sentence: The official number of casualties was about 17,000, although real numbers are thought to be above 35,000; 300,000 people were left homeless, while the financial cost of the earthquake is estimated at about 3 billion dollars.
Split into simpler sentences: The official number of casualties was about 17,000, although the numbers could be above 35,000. Three-hundred thousand people were left homeless and the financial cost is estimated at about 3 billion dollars.