What is the diameter of a trampoline with an area of 49 square ft

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

Jack did 3/5 of all problems on his weekend homework before sunday. on sunday he solved 1/3 of what was left and the last 4 problems. how many problems were assigned for the weekend?

Suppose a store sells an average of 80 cases of soda per day. assume that each case contains 24 cans of soda and that the store is open 10 hours per day. find the average number of soda that the store sells per hour.