A plumber charges $55 for a service call plus $40 per hour of work. If the total bill was $295, which equation can be solved to find $ $, the number of hours worked?
- (correct answer)
Explanation: When you encounter word problems about costs with both fixed and variable charges, you need to identify each component and how they combine to create the total cost. Here, the plumber has two cost components: a fixed service call fee of $55 (this happens once regardless of time) and an hourly rate of $40 (this depends on how many hours $ $ are worked). The total cost is the sum of these: fixed cost plus (hourly rate × hours worked) = total bill. This translates to: 55 + 40h = 295, which is choice A. The 55 is added once, and $$40h$$ represents 40 multiplied by however many hours were worked. Choice B (55h + 40 = 295) incorrectly makes the service call fee dependent on hours worked and treats the hourly rate as a fixed cost. This reverses the problem setup completely. Choice C (40h - 55 = 295) subtracts the service call fee instead of adding it. Since both the service fee and hourly charges are costs the customer pays, they must be added together, not subtracted from each other. Choice D (295h = 55 + 40) incorrectly multiplies the total bill by hours, which makes no mathematical sense in this context. The total bill is the result, not a rate. Study tip: In cost problems, always identify what's fixed (happens once) versus what's variable (depends on quantity). Fixed costs get added as constants, while variable costs get multiplied by the quantity, then everything sums to the total.