Someone please explain this

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.

What adds to be the bottom number but also multiplies to be the top number with 8 on the bottom and 15 on top

In the equation sqrt(n+5)-sqrt(11-10)=1. what is the value of n