Final answer:
The equation for a company selling a service at $3 per hour with no flat cost is y = 3x, representing a direct proportionality between total cost and hours of service.
Step-by-step explanation:
The equation to represent the business model for a company charging $3 per hour for a service with no flat cost would be a proportional equation. This means that the total cost (y) is directly proportional to the number of hours (x) of service provided. The equation can be represented as y = 3x, where y represents the total cost for the service and x represents the number of hours the service is used.
In this proportional relationship, there is no y-intercept since there is no flat fee, indicating that the line representing this equation would pass through the origin (0,0). Every additional hour of service increases the total cost by $3, reflecting the constant rate at which the company charges for its service.