10 man completed a work in 7 days,
10 women completed work in 14 days.
ie, 1 men productivity = 2 women
Hence, 5 men = 10 women
Hence, in effect we've 20 women. (5men & 10 women)
If 10women can do work in 14days, 20 women can do the same work in half the time (double number of workers) i.e 7days.