Step 1: To find out how much Ashley earns in one hour, we divide the total amount of money she earned by the number of hours she worked. She earned $105 in 5 hours, so we calculate 105 divided by 5, which equals $21. So, Ashley earns $21 per hour.
Step 2: Next, we need to find out how many hours she needs to work to make $168. Since we know that she earns $21 per hour, we divide the target earning, which is $168, by Ashley's hourly rate of $21. When we do that, we get 8 hours.
Therefore, if Ashley wants to earn $168 at the rate of $21 per hour, she should work for 8 hours.