A wholesaler sells a watch to a retailer at a gain of 37% and the retailer sells it to a customer at a loss of 25%. If the customer pays Rs 2,620.125, what had it cost the wholesaler?

For the wholesaler,

Let the cost price = Rs. $$100x$$

With profit of 37%, Selling price = $$\frac{137}{100} \times 100x = Rs. 137x$$

For the retailer,

Cost price = Rs. $$137x$$

With a loss of 25%, Selling price = $$\frac{75}{100} \times 137x = Rs. 102.75x$$

For the customer,

Cost price = $$102.75x = 2620.125$$

=> $$x = \frac{2620.125}{102.75} = 25.5$$

$$\therefore$$ Cost price for retailer = $$100 \times 25.5 = Rs. 2550$$