Answer:
13 hours
Explanation:
First you have to find the hourly rate at which money is being earned. To do so you divided the money earn ($342) by how many hours it took to earn (18 hours).
Once you do that you're given $19.00 per hour.
Now take the money earned with the unknown time ($247) and divide it by money being made per hour ($19) and you're given 13 hours