This is the 765th most frequent Czech word.
pracovní
"Pracovní" means "work" or "related to work."
In this sentence, 'pracovní' describes something relating to work, specifically the uniform that is required for a workplace.
Pracovní uniforma je povinná.
A work uniform is mandatory.
Here, 'pracovní' modifies 'doba' (hours), indicating the hours related to work or employment.
Má pracovní doba končí v pět hodin.
My working hours end at five o'clock.
In this instance, 'pracovní' pertains to the workbook, which is a book used for practice and exercises related to study or work.