I don’t understand this pls help

Ineed to learn how to solve this problem

Suppose a ball is dropped fromca height of 6ft. it bounces back up but time it bounces, it reaches only 7/10 of its pervious height. what is the total of each height that the ball reaches after 5 bounces

Which of these equations, when solved, gives a different value of x than the other three? a9.1 = -0.2x + 10 b10 = 9.1 + 0.2x c10 – 0.2x = 9.1 d9.1 – 10 = 0.2x