Can y’all help with number 16 pls

What are the soultion(s) to the quadratic equation 40- x^2=0

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?

Can someone me with the property questions for 12 13 and 14 plz