#### 6.1875
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- \( x = \frac{-460 \pm \sqrt{259,600}}{8} \)
- \( x = \frac{-460 \pm 509.5}{8} \)
- \( x = \frac{49.5}{8} = 6.1875 \)
- Question:** A tank contains 500 liters of a 30% salt solution. How much pure water must be added to reduce the concentration to 20%?
- Initial amount of salt: 500 L × 30% = 150 L of salt
- Let \( x \) be the amount of water added.
