At first,

Container A        [             ?                    ]

Container B        [             ?                    ]

After water was used,

Container A        [           5u        ][25.5]

Container B        [u][         44.5            ]

5u + 25.5 = u + 44.5

4u = 44.5 – 25.5 = 19

u = 4.75

Container B has 44.5 + 4.75 = 49.25 litres of water at first.

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