The numbers 1,2,3,4,5,6,7,8,9 are arranged in a list so that each number is either greater than all the numbers that come before it or is less than all the numbers that come before it. For example, 4,5,6,3,2,7,1,8,9 is one such list: notice that (for instance) the 6 is greater than all the numbers that come before it, and the 2 is less than all the numbers that come before it. How many such lists of the numbers 1,2,3,4,5,6,7,8,9 are possible? Be sure to include complete explanations with your answer, using complete sentences. Imagine you were going to show your solution to a classmate, and try to write your solution so that he or she could understand it without doing any extra work.
I know this qestion has been asked before but I don't fully understand any of the anweres 
