Complex sentence: In 1970,450 private and state institutions enrolled about 237,000 students, and by 1990 there were 900 institutions with about 141,000 teachers and nearly 1.5 million students.
Split into simpler sentences: In 1970,450 private and state institutions enrolled about 237,000 students. By 1990 there were 900 institutions with about 141,000 teachers and nearly 1.5 million students.