GMAT Quantitative Reasoning Practice Test 3

If the average speed from the beauty parlor is half of the average speed to the parlor then the time back from the parlor is twice the time it takes her to get to the parlor, thus 120 minutes.
The total round trip will take Naomi 60 + 120 = 180 minutes, which is 3 hours. Two round trips will take her 6 hours.