We're dividing 708129 by 21 
The aim is to understand the frequency of 21 in 708129.

Step 1:
21 can be fit into 7 0 times, resulting in a remainder of 7.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 7 to get 7.
Fetch the next digit (0) from the dividend, attach it to 7 and continue: 70 / 21

Step 2:
The number 21 fits into 70 3 times, leaving a remainder of 7.
Write down 3 as next digit of the result. 
Result so far: 3.0
If we subtract 63 from 70, we get 7.
Fetch the next digit (8) from the dividend, attach it to 7 and continue: 78 / 21

Advancing to step 3:
78 divided by 21 is 3 with a remainder of 15.
Write down 3 as next digit of the result. 
Result so far: 33.0
If we take 63 away from 78, we end up with 15.
Fetch the next digit (1) from the dividend, attach it to 15 and continue: 151 / 21

Moving on to step 4:
When dividing 151 by 21, we get 7 with a remainder of 4.
The next digit of our result is 7. 
Result so far: 337.0
Deduct 147 from 151 and we're left with 4.
Take the next digit (2) from the dividend and append it to 4, then repeat: 42 / 21

On to step 5:
21 goes into 42 2 times with a remainder of 0.
Put 2 as the next digit of the answer. 
Result so far: 3372.0
Subtract 42 from 42 to get 0.
Include the next digit (9) from the dividend after 0, then repeat: 9 / 21

Going ahead to step 6:
21 goes into 9 0 times with a remainder of 9.
The next digit of our result is 0. 
Result so far: 33720.0
If we take 0 away from 9, we end up with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 7:
21 can be fit into 90 4 times, resulting in a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 33720.4
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 8:
If we divide 60 by 21, we get 2 and a remainder of 18.
The next digit of our result is 2. 
Result so far: 33720.42
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 9:
21 goes into 180 8 times with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 33720.428
The remainder is 12 after subtracting 168 from 180.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

On to step 10:
120 divided by 21 is 5 with a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 33720.4285
If we subtract 105 from 120, we get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Moving on to step 11:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 33720.42857
If we subtract 147 from 150, we get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Advancing to step 12:
If we divide 30 by 21, we get 1 and a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 33720.428571
If we take 21 away from 30, we end up with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Moving on to step 13:
The number 21 fits into 90 4 times, leaving a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 33720.4285714
If we take 84 away from 90, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

On to step 14:
60 divided by 21 is 2 with a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 33720.42857142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

The quotient of the division is 33720.42857142, and the remainder is 1.8e-08.