In a mixture the ratio of milk and water is 7 : 5. When 56 litres of water is added to this mixture the ratio of milk and water in mixture becomes 7 : 3. Find the initial quantity of milk and water?

Let milk and water in mixture be 7x and 5x liters respectively

$frac{{7x + 56}}{{5x}} = frac{7}{3}$

35x – 21x = 168 ⇒ x = 12 liters

initial mixture = (7 + 5) ×12=144 ????????????????????????