3 men or 6 women can do a piece of work in 20 days. In how days will 12 men and 8 women do the same work ?

Answer: Option B

Let the required number of days be x
3 men = 6 women
⇒12 men = (2 × 12) women = 24 women
∴ 12 men and 8 women = (24 + 8) women = 32 women
Now, More women, Less days (Indirect Proportion)
$$\begin{array}{rl}& \therefore 32:6::20:x\\ & \iff x=\left(\frac{6\times 20}{32}\right)\\ & \iff x=\frac{15}{4}\\ & \iff x=3\frac{3}{4}\end{array}$$