Question 1191584
20 men need 60 days for the job
15 men, then the speed becomes 0.75 of what it was so  {{{60/0.75=80*days}}}.


To use some algebra,

r, the work rate of 1 man
1, for 1 piece of work or job
x, how many days



{{{20r*60=1=15r*x}}}

{{{20*60=15x}}}

{{{(20*60)/15=x}}}

{{{x=80}}}