A bag contains 56 marbles: 7 red, green, 11 yellow, 17 brown, and 13 blue. If a marble is chosen at random, what is the probability that the marble is green?

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?