Here,

M₁ = 20, D₁ =20, W₂ =$1-\frac{1}{3}$

M₂ = 20+x, D₂ = 25, W₁ = $\frac{1}{3}$

So according to the formula,

     M₁ D₁ W₂ = M₂ D₂ W₁

$$\begin{gathered} 20\times 20\times \left(1-\frac{1}{3}\right)=\left(20+x\right)\times 25\times \frac{1}{3} \\ 20\times 20\times \frac{2}{3}=\left(20+x\right)\times \frac{25}{3} \\ \Rightarrow 20+x=\frac{25}{3}\times \frac{3}{2}\times 20\times 20 \\ \Rightarrow 20+x=32 \\ x=32-20=12 men \end{gathered}$$

Hence option C is correct