Let the total quantity of liquid in the container be x litres.
Since the container has 75% milk and 25% water, the amount of milk is:
and the amount of water is:
After adding 2 litres of water, the total amount of water becomes:
Since the final condition states that milk and water are equal, we set up the equation:
0.75x − 0.25x = 2
0.50x = 2
x = 4
Milk = 0.75 × 4 = 3 litres