Haley has 16 waking hours each day to divide between working and relaxing. She currently has a job working at Chipotle, where she earns $10 per hour. For Haley, the opportunity cost of spending 1 hour of relaxing

Sanya noticed that the temperature was falling at a steady rate of 1.4 degrees every hour from the time that she first checked her outdoor thermometer. by 6 a.m., the temperature had fallen 21 degrees. which expression can you use to find how many hours earlier she had first checked the thermometer?