Complex sentence: In the China of the Yuan, or Mongol era, various important developments in the arts occurred or continued in their development, including the areas of painting, mathematics, calligraphy, poetry, and theater, with many great artists and writers being famous today.
Split into simpler sentences: In the China of the Yuan, or Mongol era, various important developments in the arts occurred or continued in their development. These developments included the areas of painting, mathematics, calligraphy, poetry, and theater, with many great artists and writers being famous today.