Time & Work Problem 12 men do a work in 36 days.In how many days can 18 men do the same work?
Sol:This can be solved as 
1 man's can do work in 12*36 days
So,1 man's 1 day work (1/12*36) days
Hence 18 men's 1 day work is (18/12*36)
So Days taken for 18 men is (12*36)/18 days.
Similarly Here is another question where i applied the same concept but i'm not getting the answer.
Q)4 men or 8 women can do a work in 24 days.How many days will 12 men and 8 women work to do same work.
My Soln:
4 men or 8 women do a work in 24 days.
so 1 man can do work in (24*4) days.
So 1 man's 1 day work is 1/(24*4)
Hence 12 men and 8 women or 16 mens can do work in 16/(24*4)
So days taken for 16 men to do work us (24*4)/16 days.
But the actual answer is 3/2 days.

4 men need 24 days
8 women need 24 days
one man needs 96 days [4*24]
one woman needs 192 days [8*24]
so 12 men and 8 women need 6 days [192 / (96 / 12 + 192 / 8)]
==> 192 / ((4 * 24) / 12 + (8 * 24) / 8) = 6
