Share 80 in ratio 5:3

Giuseppi's pizza had orders for $931.00 of pizzas. the prices were $21 for a large pizza, 514 for a medium pizza, and $7 for a small pizza. the number of large pizzas was two less than four times the number of medium pizzas. thenumber of small pizzas was three more than three times the number of medium pizzas. how many of each size of pizza were ordered?

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

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?