Answer: 157.5 hours per month
Explanation:
Given: An employee works 21 days per month. If they work an average of 7.5 hours per day.
i.e. The number of days an employee works in a month =21
The average hours an employee works in a day=7.5 hours
Then, the total hours they work in a month =

i.e. The total hours they work in a month = 157.5 hours
Hence, They work 157.5 hours per month.