K men agree to donate a gift of Rs. L to trust. If three men drop out how much more will each have to contribute towards the purchase of the gift ?

Intial contribution = L/K
After 3 men drop, then contribution =L/K-3
The amount more to pay in contribution =  $\frac{L}{K-3} - \frac{L}{K}$

=  $\frac{3L}{K(K-3)}$