Given: A stationery dealer sells a premium pen at an 8% loss and a reference book at a 20% profit. The overall profit from the first transaction = ₹12. Later, the pen is sold at an 8% profit and the book at a 15% profit. The revised total profit is ₹8 more than the earlier profit. To find: Cost prices of the pen and the book. Formula Used: Profit = CP × Profit%/100 Loss = CP × Loss%/100 Net Profit = Profit - Loss Calculation: Let the cost price of the pen = ₹x and the cost price of the book = ₹y. Under the first arrangement: ⇒ Loss on pen = 8x/100 ⇒ Profit on book = 20y/100 ⇒ 20y/100 - 8x/100 = 12 ⇒ 20y - 8x = 1,200 ⇒ 5y - 2x = 300 ...(1) Under the revised arrangement, total profit increases by ₹8: ⇒ Revised profit = ₹12 + ₹8 ⇒ Revised profit = ₹20 Therefore: ⇒ Profit on pen + Profit on book = ₹20 ⇒ 8x/100 + 15y/100 = 20 ⇒ 8x + 15y = 2,000 ...(2) From equation (1): ⇒ 5y - 2x = 300 ⇒ 10y - 4x = 600 Multiplying equation (2) by 1: ⇒ 8x + 15y = 2,000 Solving the two equations: ⇒ x = ₹78.57 approximately ⇒ y = ₹91.43 approximately ∴ The cost prices are approximately ₹78.57 and ₹91.43, respectively.