If the price of eraser is reduced by 25%. A person can buy 2 more erasers for a rupee. How many erasers are available for a rupee after reduction ?

Let n erasers be available for a rupee
Reduced Price $$ = \frac{{75}}{{100}} \times 1 = \,\frac{3}{4}$$
$$\frac{3}{4}$$ rupee fetch n erasers = 1 Rupee will fetch $$\left( {{\text{n}} \times \frac{4}{3}} \right)$$  erasers
Therefore,
$$\eqalign{ & \frac{{4n}}{3} = n + 2 \cr & \Rightarrow 4n = 3n + 6 \cr & \Rightarrow n = 6 \cr} $$
Now total number of erasers are available for a rupee = 6 + 2 =8