Can someone help me I literally don’t get this whole part.

Abbey purchased a house using a fixed rate mortgage. the annual interest rate is 4.2% compounded monthly for 20 years. the mortgage amount is $235,000. what is the monthly payment on the mortgage? this isn't a multiple choice question have to show my work

If f(x)=2x-6 and g(x)=3x+9, find (f-g)(x)

The function f(x) = 14,600(1.1)* represents the population of a town x years after it was established. what was the original population of the town?