Explanation:

- Initially, the container has 160 liters of milk.

- Some milk is replaced by water such that milk is now three times the water.

- Let x be the liters of milk replaced. Then, milk = 160 - x and water = x.

- Given: \(160 - x = 3x\)

- Solving, \(160 = 4x\) ? \(x = 40\)

- Thus, milk = 120 liters and water = 40 liters.

- 20 liters of this mixture is replaced by 15 liters of water.

- Initial ratio: Milk:Water = 120:40 = 3:1

- In 20 liters, milk = 15 liters, water = 5 liters.

- After replacement, milk = 120 - 15 = 105 liters

- Water = 40 - 5 + 15 = 50 liters

Correct Answer: Option 2: 50 liters