Can someone help me please

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?

Two numbers have a sum of -19. one number is x. what expression represents the other number?

Annabelle's homework is 75% it took her three hours how long should she estimate it will take her to complete her homework.