Y=? cm plz hellp will give brainest

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)

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?

Need so much on this one how many yards?