if you deposit $3000 into saving account paying 8% annual interest compounded monthly how much money would be in the account after 15 years

Let the closed interval [a , b] be the domain of function f. the domain of f(x - 3) is given by (a) the open interval (a , b) (b) the closed interval [a , b] (c) the closed interval [a - 3 , b - 3] (d) the closed interval [a + 3 , b + 3]

Which of the following is best modeled using a linear equation y=ax+b, where a is less than 0?

Ineed with question three. i don't understand how i'm supposed to achieve 3 marks.