[{"_id":{"$oid":"61fb6bf71be79c03227d6bbf"},"id":"17202155","completed":["cse331","cse312"],"incompleted":[{"name":"math","preReq":["bang","eng"]},{"name":"science","preReq":["bang","eng","math"]},{"name":"astronomy","preReq":["bang","eng","science","math"]}]}]

db.collection.update({id:"17202155"},{$pull:{"incompleted.$[].preReq":"math"}})/** "incompleted": { name: "math"}*/