Complex sentence: In 1900, there were only 8.7 million adherents of Christianity in Africa; and in 2010 there are 390 million, and it is expected that by 2025 there will be 600 million Christians in Africa.
Split into simpler sentences: In 1900, there were only 8.7 million adherents of Christianity in Africa, while in 2010 there were 390 million. It is expected that by 2025 there will be 600 million Christians in Africa.