In a mixture of milk and water, there is only 26% water. After replacing the mixture with 7 liters of pure milk , the percentage of milk in the mixture become 76%. The quantity of mixture is:

• Let the quantity of the original mixture be x liters.
• Water in the mixture = 26% of x = 0.26x
• Milk in the mixture = 74% of x = 0.74x
• 7 liters of pure milk is added ⇒ New milk = 0.74x + 7
• Total new quantity = x + 7
• New percentage of milk = 76%

Form the equation:

(0.74x + 7) / (x + 7) = 0.76

Cross-multiply:

0.74x + 7 = 0.76(x + 7)
0.74x + 7 = 0.76x + 5.32

Bring like terms together:

7 - 5.32 = 0.76x - 0.74x
1.68 = 0.02x
x = 1.68 / 0.02 = 84

So original mixture = 84 liters
New total mixture = 84 + 7 = 91 liters

Answer: 91 liters

The quantity of the new mixture is 91 liters.