Step by step solution :

	1	C	D	D
-	0	A	7	0

Step-1 : D - 0
Here D=13 `>` 0, so directly subtract it
`=13-0`
`=13`
`=D_16`

	1	C	D	D
-	0	A	7	0
				D

Step-2 : D - 7
Here D=13 `>` 7, so directly subtract it
`=13-7`
`=6`
`=6_16`

	1	C	D	D
-	0	A	7	0
			6	D

Step-3 : C - A
Here C=12 `>` A=10, so directly subtract it
`=12-10`
`=2`
`=2_16`

	1	C	D	D
-	0	A	7	0
		2	6	D

Step-4 : 1 - 0
Here 1 `>` 0, so directly subtract it
`=1-0`
`=1`
`=1_16`

	1	C	D	D
-	0	A	7	0
	1	2	6	D

Step by step solution :

	2	0	C
-	0	7	E

Step-1 : C - E
Here C=12 `<` E=14, we take borrow from 0, which takes borrow from 2
So 2 becomes 1, 0 becomes 15 and C=12 becomes 12+16=28
`=28-14`
`=14`
`=E_16`

		15
	1	16	28
	2	0	C
-	0	7	E
			E

Step-2 : F - 7
Here F=15 `>` 7, so directly subtract it
`=15-7`
`=8`
`=8_16`

		15
	1	16	28
	2	0	C
-	0	7	E
		8	E

Step-3 : 1 - 0
Here 1 `>` 0, so directly subtract it
`=1-0`
`=1`
`=1_16`

		15
	1	16	28
	2	0	C
-	0	7	E
	1	8	E

Step by step solution :

	7	F	0	E	B
-	0	F	7	6	4

Step-1 : B - 4
Here B=11 `>` 4, so directly subtract it
`=11-4`
`=7`
`=7_16`

	7	F	0	E	B
-	0	F	7	6	4
					7

Step-2 : E - 6
Here E=14 `>` 6, so directly subtract it
`=14-6`
`=8`
`=8_16`

	7	F	0	E	B
-	0	F	7	6	4
				8	7

Step-3 : 0 - 7
Here 0 `<` 7, we take borrow from F
So F=15 becomes 14 and 0 becomes 0+16=16
`=16-7`
`=9`
`=9_16`

		14	16
	7	F	0	E	B
-	0	F	7	6	4
			9	8	7

Step-4 : E - F
Here E=14 `<` F=15, we take borrow from 7
So 7 becomes 6 and E=14 becomes 14+16=30
`=30-15`
`=15`
`=F_16`

		30
	6	14	16
	7	F	0	E	B
-	0	F	7	6	4
		F	9	8	7

Step-5 : 6 - 0
Here 6 `>` 0, so directly subtract it
`=6-0`
`=6`
`=6_16`

		30
	6	14	16
	7	F	0	E	B
-	0	F	7	6	4
	6	F	9	8	7