Question 758411
Account for the number of hours!  The work needs the one man to do the task for a set number of hours.


8 hours per day times 30 days = the set number of hours
{{{8*30=240}}} hours.


Now the man works only 5 hours per day, so he still must work 240 total hours to do the job.
{{{5*d=240}}} using d for the number of days.