Pls answer all the question pls

Find all the values of x that make 0.1x + 0.25(102 - x) < 17.10 true.

Standard deviation of 19,29,21,22,23

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?