Question 857648
Uniform rates for task completion, R*T=J, rate, time, quantity of jobs.  Your example has J=1.  The job is, "paint a house".


The first clause gives the rate for 6 men as {{{1/21}}} jobs per day.  The rate for just 1 man alone is {{{(1/6)(1/21)}}} jobs per day.


Now you want a number of men, N, to spent 14 days to do the one job.
{{{highlight(N(1/(6*21))*14=1)}}};
and you are asked, what is N.