If 5 men or 8 women can do a piece of work in 42 days, in how many days can 10 men and 5  women do the same work?

5 Men or 8 Women = 42 days

10 men and 5 women completes the same work in ? 

capacity of 5 men=capacity of 8 women

then,capacity of 10 men=capacity of 16 women

$8w$$\times 42=(16w+5w)\times d$      ($m1\times d1=m2\times d2$)

$8w$$\times 42=21w\times d$

d=16days