I'm not 100% sure if I'm doing it the right way, but I think the answer is the factorial of the number of letters divided by the factorials of the number of elements of each kind of element (in this case, the same letters)
The statement which is true in the choices is the third item in the choices such as "Nina makes 20x dollars at the clothing store each week". It was clearly stated in the given that x represent the total number of hours she worked in a week. This statement made the other items in the choices wrong.