Hi,

1. I would clarify first whether its hairdressers for men / women / both
2. Estimate the corresponding population size (probably discount very young kids)
3. Adjust the population size by the tourists, people coming from closer cities, etc.
4. Estimate the average frequency of services per person (depending on the segment - men, women, etc)
5. Estimate the total demand of services per day (Average frequency * population / number of days between the haircuts)
6. Calculate the capacity of the average Hair Dresser (8 hours / 1 hr per haircut)
7. Take into account idle time (e.g. your actual Hairdresser occupancy = total capacity / 2 assuming 50% idle time)
8. Divide the total demand by the occupancy of 1 hairdresser

Best