Explanation:

FOR MEN -

3 men complete work in 16 days

So 3 men one day work= 1/16

1 men one day work = 1/16×3

FOR WOMEN

4 women complete work in 16 days

So 4 women one day work= 1/16

1 women one day work = 1/16×4

Now we have to find when both (12 Men & 8 Women) are working together

So 12 Men one day work = 12 × (one day work of one man)

=12 × (1 / 16×13) =1/4

So 8 Women one day work = 8 × (one day work of one woman)

= 8 × (1 / 16×4) =1/8

Adding one day of (12 Men) & (8 Women)

= (1/4) + (1/8) = 3/8

This means 12 Men and 8 Women does 3/8 fraction of work in one day

Thus they would complete the work in 8/3 days.

Hence, option 3 is the correct answer.