At least 40 pounds of fertilizer is needed to adequately cover your backyard. let f = the amount of fertilizer needed.

Really need on these. i have no idea what to do

Jack has a piece of red ribbon that is two times as long as his piece of blue ribbon. he says that he can use two different equation to find out how long his piece of red ribbon is compared to his piece of blue ribbon is. is he correct? explain his reasoning

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