stephanie accidentally hit a golf ball through her neighbors square window with the side length x. she needs to buy a new piece of glass to replace the one she broke.

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?