1. **Stating the problem:** A retailer bought 6 watches for a total of 3330 and sold each watch at a gain of 111. We need to find the selling price of each watch. 2. **Formula and explanation:** - Cost price (CP) of one watch = Total cost / Number of watches = $\frac{3330}{6}$ - Gain per watch = 111 - Selling price (SP) per watch = Cost price + Gain 3. **Calculations:** - Calculate cost price per watch: $$CP = \frac{3330}{6} = 555$$ - Calculate selling price per watch: $$SP = CP + Gain = 555 + 111 = 666$$ 4. **Answer:** The retailer sold each watch at 666.