Okay so in total there is 180 feet. The person travels 24 feet every 7 seconds. So, you would divide 180 by 24. You should get the answer 7.5 so seven and a half seconds. Now multiply 7.5 by 7 you should get 52.5 seconds.
I'm pretty sure this is how you would find the answer to that, if I'm wrong let me know.