Answer:
1. $ 272
2. 11 hours
Step-by-step explanation:
Given the below equation;

where C = the total cost
h = hours spent
1. If h = 7 hours, let's go ahead and find C;

So if it takes 7hours to fix the drain, the total cost will be $272.
2. If C = $384, let's go ahead and find h;

So if the plumber charged $384 to fix the drain, it means that he'd spent 11 hours to fix the drain.