1. The problem asks: How much do you pay for four tubes of toothpaste if the offer is "2+1 GRATIS" and each tube costs 1.39 euros? 2. The "2+1 GRATIS" means if you buy 2 tubes, you get 1 tube free. So for every 3 tubes, you pay only for 2. 3. To find the cost for 4 tubes, split them into groups: - First 3 tubes: pay for 2 tubes - The 4th tube: pay for 1 tube 4. Calculate the total cost: $$\text{Total cost} = 2 \times 1.39 + 1 \times 1.39 = 3 \times 1.39$$ 5. Multiply: $$3 \times 1.39 = 4.17$$ 6. Therefore, you pay 4.17 euros for 4 tubes of toothpaste under the "2+1 GRATIS" offer.