9 men build a house in a working 4 days .how many workmen ,working at the same rate willbe needed to build a house in 3 days

Answer 1

9 men do the job in 4 days
That means 9 men can do 1/4 the job in 1 day.
So, each man can do 1/36 of the job in a day.

So, each man can do 3/36 = 1/12 the job in 3 days

So, it will take 12 men to do the job in 3 days

Or, more succinctly, since we want to take 3/4 as long, it will take 9/(3/4) = 12 men

Answer 2

18-10x<-22