B^-2 b^4 please help me with this

If f(x) =3x-2 and g(x) =2x+1 fins (f+ g) (x)

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.

Ineed with number 6 , explain how to get 1978