Question

the starting temperature was 0 degrees c. then it dropped 4 times until it was colder than -20 degrees c. which inequality expresses the number, d, by which the temperature could have dropped each time? -4d greater than or equal to -20, -4d<-20, -4d>-20, -4d less than or equal to -20

Answer 1

If the temperature drops by d each time, after 4 drops the temperature is 0 − 4d = −4d. "Colder than −20°C" means −4d < −20. So the correct inequality is −4d < −20. (Equivalently, d > 5.)