Question 813537
First look at the one man rate per hour.
9 men for 5*16 hours_____________________1 man for 9*5*16 hours because one man must work 9 times longer.
{{{1/(9*5*16)}}}  jobs per hour.


Now, 18 men work at the rate of {{{18/(9*5*16)}}} jobs per hour.
FIVE hours?
How much of the job?
{{{(18/(9*5*16))*5}}} jobs.  This is {{{18/(9*16)=2/16=1/8}}} job.  That is for 1 day, 5 hours per day.  


Using that rate as (1/8) job per day, how many days for 1 whole job?
Let d = number of days.
{{{(1/8)*d=1}}}
{{{highlight(d=8/1)}}} or 8 days.