Final answer:
The correct equation representing the cost, y, after x hours of service from a plumber with specific charges is y = 50x + 25; where y is the total cost, x is the hours of service, 25 is the y-intercept, and 50 is the slope.
Step-by-step explanation:
The student is tasked with writing an equation to represent the cost, y, after x hours of service from a plumber who charges a $25 service call plus $50 per hour. To create this equation, we start with the $25 service fee, which is a fixed amount, and then add $50 for each hour of service provided by the plumber.
Therefore, the total cost can be written as y = 50x + 25. Here, x represents the number of hours of service, which is the independent variable, and y represents the cost of the service, which is the dependent variable. The number 25 is the y-intercept, indicating the initial charge before any hourly service is added. The number 50 is the slope of the equation, representing the charge per hour of service.