Making a list can help you solve a math problem because it shows you the information you will be using.
Sally is 13 years old. Sally's brother Mark is twice as old as Sally. Sally's older sister Daffy is the sum of Sally and Mark's age. How old is Daffy?
making a list in this question tells you all of the different ages and lists them out in a row.
The answer is 46 thank you
Texaschic nailed it when saying that it's arithmetic
The recursive way to write this is to say


which tells us "start at 6 and each time subtract off 5"
The

portion is the nth term while

is the term just before the nth term