Answer:
10 hours costs $180.
Explanation:
We know that:
- The service charges $15 per hour plus a fixed fee, which is unknown.
- For 3 hours charges $75.
So, using this data we can form the relation for the problem:
; where b is the unknown fixed fee.
Solving for b:

With this result, the explicit linear equation would be:
; where x is hours and y is the total cost.
For 10 hours would be:

Therefore, for 10 hours the charge is $180.