Effort of 900M + 500W in 2 weeks is equivalent to effort of 1200M + 250W in 3 weeks.
So (900M + 500W) X 2 = (1200M + 250W) X 3
36M = 5W
Therefore,W = (36M)/5
Required number of men = x to do the same task in 1 week.
So (900M + 500W) X 2 = (xM) X 1 [ substitute W = (36M)/5 ]
Solving, x = 9000.
So 9000 men are needed to do the same task in 1 week.