Ineed with this question and i need an answer by thursday 10-24-19 at 11: 59 pst. and this is algebra 1

For a field trip to the zoo, 4 students rode in cars and the rest filled nine busess. how many students were in each bus if 472 students were on the trip

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

Zoey made 5 1/2 cups of trail mix for a camping trip. she wants to divide the trail mix into 3/4 cup servings. a. ten people are going on the trip. can zoey make enough 3/4 cup servings so that each person gets one serving? b. what size would the servings need to be for everyone to have a serving?