Verified answer

Start with 12 liter jug full. Fill up the 8 liter jug. Use the 8 liter jug to fill up the 5 liter jug. You have 4 (12jug) 3 (8jug) and 5 (5jug) in the jugs.

Next, pour the 5 liters in the 5jug into the 12jug. You have 9/3/0.

Then, pour the 3 liters in the 8jug into the 5 jug. You have 9/0/3.

Then, fill up the 8jug with the 12jug. You have 1/8/3.

Then, top off the 5jug with the 8jug. You have 1/6/5.

Finally, pour the 5jug into the 12 jug. You have 6/6/0.