PLEASE HELP ME!! please explain your answer so I know how to do it next time! The question is number 7

Awrestling tournament begins with 128 competitors. in the first round, each competitor has 1 match against another wrestler. the winner of each match moves on to the next round until there is a winner. write a sequence in which the terms represent the number of players still in the tournament at the end of each round. describe the sequence? how many rounds are in the tournament?

Anne is twice as old as bill, and bill is 3 years older than christie. the sum of anne s and christie s ages equal 72. find their age difference.?

We just started the introduction into circles and i have no idea how to do this.