The Shopkeeper's Profit

$\text{Let the real price of the product be `x'.} \\ \text{Since he sold at a loss, real price will be greater than selling price, so:} \\ x - \dfrac{20}{100}x = 480 \\ \dfrac{100x - 20}{100} = 480 \\ 100x - 20x = 48000 \\ 80x = 48000 \\ \fbox{ x = 600 } \\ \text{Therefore if he needs to sell at a 20\% profit, } \\ \text{Profitable Selling Price = } x + \dfrac{20}{100}x = 600 + \dfrac{20}{100}600 = 600 + 120 \\ = \fbox{ 720 }$

as he sold the product for $480$ $ on $20$ % loss,

so, the original cost was= $\frac{100 \times 480}{80}$ = $600$ $

so now, $20$ % discount on original cost will be= $\frac{600 \times 20}{100}$ = $120$ $

so,on $20$ % discount, he will sell it on= $600+120=720$ $