There will still be 34.5 L of water in the two pails combined because no water is lost.
Thus the total remains 34.5 L after transferring water between them.
Let the final amount in the smaller pail be x.
Then the larger pail contains 9x.
So x + 9x = 34.5.
That simplifies to 10x = 34.5.
Dividing both sides by 10 gives x = 3.45.
Therefore the smaller pail held 3.45 L at the end.
Because 0.68 L was poured into it, its initial volume was 2.77 L (3.45 minus 0.68)
We can also deduce the larger pail initially contained 31.73 L
(either 35 minus 2.77, or 9 times 3.45 plus 0.68)