Let's assume the cost price of the watch was Rs. X.
When Naresh sold the watch at a 5% loss, he sold it for 95% of the cost price, which is 0.95X.
If he had sold it for Rs. 104 more, the selling price would have been (0.95X + 104).
According to the second scenario, he would have gained 8%, which means the selling price would be 108% of the cost price, which is 1.08X.
Now we can set up the equation:
0.95X + 104 = 1.08X
Solving for X:
0.13X = 104
X = 104 / 0.13
X = 800
So, the cost price of the watch was Rs. 800, and the selling price is 0.95X, which is 0.95 * 800 = Rs. 760