Problem Page A child is running on a moving sidewalk in an airport. When he runs against the sidewalk's motion, he travels 35ft in 7 seconds. When he runs with the sidewalk's motion, he travels 143ft

Problem Page A child is running on a moving sidewalk in an airport. When he runs against the sidewalk's motion, he travels 35ft in 7 seconds. When he runs with the sidewalk's motion, he travels 143ft in 11 seconds. What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk?