Can some one help as i realy dont get this

For each proportion find the unknown number x 1/5/8=×/15

The swimming pool is open when the high temperature is higher than 20∘c. lainey tried to swim on monday and thursday (which was 33 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 33 days. write an inequality to determine the rate of temperature decrease in degrees celsius per day, d, from monday to thursday.

School has 204 sixth grade students. if the sixth grade is 30% of the total school, how many students are in the middle school?