Asporting goods store ordered 144 cans if tennis balls

Omar is going on a road trip! the car rental company offers him two types of cars. each car has a fixed price, but he also needs to consider the cost of fuel. the first car costs $90 to rent, and because of its fuel consumption rate, there's an additional cost of s0.50 per kilometer driven.

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

Solve for n? [tex]z = \frac{3}{4} mn[/tex]