How do you solve capacity?

Amuffin recipe, which yields 12 muffins, calls for cup of milk for every 1 cups of flour. the same recipe calls for cup of coconut for every cup of chopped apple. to yield a batch of 30 muffins, how much flour will be needed in the mix?

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

There are 3232 forwards and 8080 guards in leo's basketball league. leo must include all players on a team and wants each team to have the same number of forwards and the same number of guards. if leo creates the greatest number of teams possible, how many guards will be on each team?