1. **Stating the problem:** We need to find the cost of 20 litres of a paint mixture where white and blue paints are mixed in the ratio 3:2. 2. **Understanding the ratio:** The ratio 3:2 means for every 3 parts of white paint, there are 2 parts of blue paint. 3. **Total parts in the mixture:** Total parts = 3 + 2 = 5 parts. 4. **Finding the volume of each paint:** Since the total mixture is 20 litres, $$\text{Volume of one part} = \frac{20}{5} = 4 \text{ litres}$$ 5. **Volume of white paint:** $$3 \times 4 = 12 \text{ litres}$$ 6. **Volume of blue paint:** $$2 \times 4 = 8 \text{ litres}$$ 7. **Cost of white paint:** $$12 \times 2.80 = 33.60$$ 8. **Cost of blue paint:** $$8 \times 3.50 = 28.00$$ 9. **Total cost of the mixture:** $$33.60 + 28.00 = 61.60$$ **Final answer:** The cost of 20 litres of the mixture is 61.60. **Is the question correct?** Yes, the question is correct and the solution steps are accurate. The ratio and cost calculations are properly applied.