Final answer:
The plumber worked for 3.5 hours, after subtracting the one-time call out fee of $65 from the total bill of $327.50 and dividing the remaining amount by the hourly rate of $75.
Step-by-step explanation:
The student is asking us to calculate the number of hours the plumber must have worked given the total bill amount. The plumber charges a one-time call out fee of $65, plus $75 per hour of work. The total bill was $327.50.
To find out the number of hours worked, we first need to subtract the one-time call out fee from the total bill:
Total bill - One-time fee = $327.50 - $65 = $262.50
Now that we have the total amount that corresponds to hourly work, we can determine the number of hours by dividing this amount by the hourly rate:
Amount for hourly work ÷ Hourly rate = $262.50 ÷ $75
When you perform this division, you get 3.5. So, the plumber worked for 3.5 hours.