Which statement are true regarding the diagram?

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?

What is the value of x when x + 7 = 21?

If x-1 and x+3 are the factors of x3+10x2+ax+b find a and b