1. You go into the activity and press DECLINE. 
  2. A notification will be sent saying that you no longer will participate in the activity. 
  3. If the request is about a FIX activity then it will automatically be opened again and a new request will be sent to those that have not yet accepted or not responded to the request.
  4. If the request is a pickup / drop off of a person, that person also receives a notification.
  5. For SYNC activities, a notification is sent to the person who invited to the activity, to anyone who has accepted or has not yet responded to the request.