[{"age":18,"role":"client","_id":"61a65b0a64f8cf0020111582","answers":[{"_id":"61a65b0a64f8cf0020111583","position":1},{"_id":"61a65b0a64f8cf0020111583","position":2}],"__v":0},{"age":18,"role":"client","_id":"61a65b0a64f8cf0020111584","answers":[],"__v":0}]

db.collection.update({"_id":"61a65b0a64f8cf0020111582"},{"$push":{"answers":{"position":3}}})