90 hours per week is equivalent to 12.86 hours per day, assuming a 7-day work week.

To arrive at this answer, you can use basic arithmetic to divide the total number of hours per week by the number of days in a week:
90 hours per week / 7 days per week = 12.86 hours per day
It is important to note that working 90 hours per week is an extremely high number of hours and can lead to negative health effects such as fatigue, stress, and burnout. The World Health Organization (WHO) recommends that adults work no more than 48 hours per week to avoid these negative health impacts.
In some industries, such as healthcare or emergency services, it is not uncommon for workers to work long hours or overtime. However, it is important for employers to ensure that their workers are not overworked and that they have adequate time off to rest and recover.
In conclusion, 90 hours per week is equivalent to 12.86 hours per day, assuming a 7-day work week. However, working such long hours can have negative health impacts and it is important for employers to ensure that their workers are not overworked and have adequate time off.