If you would like to know how much milk is required to fill the jug, you can calculate this using the following steps:
1/3 of a liter of milk ... 1/9 of a jug of tea
x liters of milk = ? ... 1 jug of tea
1/3 * 1 = 1/9 * x
1/3 = 1/9 * x /*9
1/3 * 9 = x
x = 3 liters of milk
The correct result would be 3 liters of milk.