Step by step solution :

	6	4	3
-	0	3	3

Step-1 : 3 - 3
Here 3 `=` 3, so directly subtract it
`=3-3`
`=0`

	6	4	3
-	0	3	3
			0

Step-2 : 4 - 3
Here 4 `>` 3, so directly subtract it
`=4-3`
`=1`

	6	4	3
-	0	3	3
		1	0

Step-3 : 6 - 0
Here 6 `>` 0, so directly subtract it
`=6-0`
`=6`

	6	4	3
-	0	3	3
	6	1	0

Step by step solution :

	1	6	9	0
-	0	6	3	5

Step-1 : 0 - 5
Here 0 `<` 5, we take borrow from 9
So 9 becomes 8 and 0 becomes 0+10=10
`=10-5`
`=5`

			8	10
	1	6	9	0
-	0	6	3	5
				5

Step-2 : 8 - 3
Here 8 `>` 3, so directly subtract it
`=8-3`
`=5`

			8	10
	1	6	9	0
-	0	6	3	5
			5	5

Step-3 : 6 - 6
Here 6 `=` 6, so directly subtract it
`=6-6`
`=0`

			8	10
	1	6	9	0
-	0	6	3	5
		0	5	5

Step-4 : 1 - 0
Here 1 `>` 0, so directly subtract it
`=1-0`
`=1`

			8	10
	1	6	9	0
-	0	6	3	5
	1	0	5	5

Step by step solution :

	4	6	4
-	2	9	6

Step-1 : 4 - 6
Here 4 `<` 6, we take borrow from 6
So 6 becomes 5 and 4 becomes 4+10=14
`=14-6`
`=8`

		5	14
	4	6	4
-	2	9	6
			8

Step-2 : 5 - 9
Here 5 `<` 9, we take borrow from 4
So 4 becomes 3 and 5 becomes 5+10=15
`=15-9`
`=6`

		15
	3	5	14
	4	6	4
-	2	9	6
		6	8

Step-3 : 3 - 2
Here 3 `>` 2, so directly subtract it
`=3-2`
`=1`

		15
	3	5	14
	4	6	4
-	2	9	6
	1	6	8