56 men can complete a piece of work in 24 days. In how many days can 42 men complete the same piece of work ?

Answer: Option B

Let the required number of days be x
Less men, More days (Indirect proportion)
$$\begin{array}{rl}& \therefore 42:56::24:x\\ & \iff 42\times x=56\times 24\\ & \iff x=\left(\frac{56\times 24}{42}\right)\\ & \iff x=32\end{array}$$