Atrain travels 24 miles in 30 minutes. calculate it's speed in mph

Acircular city park has a sidewalk directly through the middle that is 111 - feet long. if each bag of fertilizer covers 50 square feet, then determine how many bags of fertilizers the parks and recreation department needs to use to cover the circular park. ignore all the sidewalks around and through the park.

Select the sequences that are geometric.

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?