Answer: OPTION D
Let ratio of population X to population Y (Pold) = $\frac{Px}{Py}$ = P
New Population of X = $Px+ \frac{(x*Px)}{100}$ = $(1+\frac{x}{100})Px$
New Population of Y = $Py+ \frac{(y*Py)}{100}$ = $(1+\frac{y}{100})Py$
Ratio of new population of x and y (Pnew) =$\frac{(100+x)Px }{(100+y)Py }$ = $\frac{(100+x)P}{(100+y)}$
Percentage increase in P = (Pnew -Pold)/Pold = $\frac{ \frac{(100+x)P }{(100+y)} -P }{P}$ $\times 100$
=($\frac{(100+x) }{(100+y)}$ -1) $\times 100$
= $\frac{x-y}{100+y} \times 100$
=$100\frac{(x-y)}{100+y}$