Question 885169
25*32=800
it takes 800 man days to finish the job
8*25=200
in 8 days they used 200 man days
800-200=600
so they need 600 more man days to finish the job.
600/20=30 more days  to finish the job

checking out reasonableness.
if the 25 continued they would take 24 more days so it is reasonable that it would take 20 men 30 days to finish