Answer:
it is a 7 step process explained in explanation section
Explanation:
Step one
fill 7 litre bucket then pour it in 4 liter bucket
output: 7 litre bucket has 3 litres and 4 litres bucket has 4 liter in it
Step two
drain four liter bucket and pour 3 liter from 7 litre bucket in it
output: 7 litre bucket has 0 litres and 4 litres bucket has 3 liter in it
step 3
fill 7 litre bucket and transfer water from it in 4 liter bucket which has already 3 liter in it
output: 7 litre bucket has 6 litres and 4 litres bucket has 4 liter in it
step 4
drain four liter bucket and pour 4 liter from 7 litre bucket which has 6 litre in it
output: 7 litre bucket has 2 litres and 4 litres bucket has 4 liter in it
step 5
drain 4 litre bucket and pour 2 litre from 7 litre bucket
output: 7 litre bucket has 0 litres and 4 litres bucket has 2 liter in it.
step 6
fill 7 liter bucket fully
output: 7 litre bucket has 7 litres and 4 litres bucket has 2 liter in it.
step 7
pour water from 7 liter bucket in 4 litre bucket which has already 2 litre in it
output: 7 litre bucket has 5 litres and 4 litres bucket has 4 liter in it.