Question 774170
64 men, 1 job, 15 days.
1 man, 1 job, {{{64*15}}} days = 975 days.
The one-man rate is {{{1/975}}} jobs per day.


How many men, n, need 12 days to do this job?
{{{highlight(n(1/975)*12=1)}}} which is rate*time=jobs, and {{{n(1/975)}}} is the rate for this number of men doing the job.


Solving for n, the count of the men in the 12-day group,
{{{n=975/12}}}
{{{n=81&1/4}}} men, but you cannot use a fraction of a man.  Round-up makes more sense.  Choose 82 men.


How many more men than 64 is n?  
{{{82-64=18}}} more men.