4 men or 7 women can do a work in 40 days. In how many days 8 men and 6 women can do that work.

One day work of 4 men $=\frac{1}{40}$

One day work of 1 man$=\frac{1}{160}$

One day work of 7 women $=\frac{1}{40}$

One day work of 1 women $=\frac{1}{280}$

One day work of 8 men $=8\times \frac{1}{160}=\frac{1}{20}$

One day work of 6 women$=6\times \frac{1}{280}=\frac{3}{140}$

One day work 8 men and 6 women

$\Rightarrow \frac{1}{20}+\frac{3}{140}\Rightarrow \frac{7+3}{140}=\frac{10}{140}=\frac{1}{14}$

Hence, 8 men and 6 women can complete the work in 14 days