While selling a router, a shopkeeper gives a discount of 15%. If he gives a discount of 20%, he earns Rs. 51 less as profit. What is the original marked price of the router?

Let the marked price of the router be Rs. P

From the given data,

$P x \frac{85}{100} - P x \frac{80}{100} = 51P x \frac{5}{100} = 51\Rightarrow P = \frac{5100}{5} = 1020$

Hence, the original marked price of the router is Rs. 1020.