Correct Answer - Option 1 : 36 litres

**Calculation:**

Let the quantity of milk and water be 6x and 5x litres respectively,

According to the question,

6x/(5x + 12) = 6/7

⇒ 42x = 30x + 72

⇒ 42x - 30x = 72

⇒ 12x = 72

⇒ x = 6

The quantity of milk = 6x = 6 × 6 = 36 litres

the quantity of water = 5x = 5 × 6 = 30 litres

**∴ The quantity of milk is 36 litres.**