Simplify the following text for a Grade 7 native English-speaking person.
Original: Ibn SÄ `` nÄ wrote almost 450 treatises on a wide range of subjects , of which around 240 have survived .
Simplified: Ibn SÄ `` nÄ studied medicine under a physician named Koushyar . He wrote almost 450 treatises on a wide range of subjects , of which around 240 have survived .