Hi:) my teacher taught this in class , she gave me the solution to this question but I don’t understand it at all. Anyone able to explain it fully , instead of just providing the solutions ? Thank you so much :)

Select all the correct answers. what is 221,000,000,000,000,000,000 expressed in scientific notation?

The swimming pool is open when the high temperature is higher than 20∘c. lainey tried to swim on monday and thursday (which was 3 days later). the pool was open on monday, but it was closed on thursday. the high temperature was 30∘c on monday, but decreased at a constant rate in the next 3 days. write an inequality to determine the rate of temperature decrease in degrees celsius per day, d, from monday to thursday.

Select the margin of error that corresponds to the sample mean that corresponds to each population: a population mean of 25, a standard deviation of 2.5, and margin of error of 5%