Ared string of holiday lights blinks once every 3 seconds while a string of blue lights blinks once every 4 seconds. how many times will both sets of lights blink at the same time in one minute?

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?