Answer:
About 4.5 hours, you can say 5 hours
Explanation
You can solve this by constructing a linear equation, which would turn out like this, 25x+60=172.50. How I got this is that it says his charge is 25 per hour, that is basically multiplication by an unknown number, so put that as a variable. Next it says he has a service fee of 60 dollars, this is what's called an initial fee. Now all we need to do is solve for x, which turns into 4.5. I don't know if they ask to round your answer or something, I hope this is right.