640629 ÷ 20 
The aim is to understand the frequency of 20 in 640629.

Let's proceed to step 1:
The number 20 fits into 6 0 times, leaving a remainder of 6.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Append the next digit (4) from the dividend to 6 and continue with: 64 / 20

Let's proceed to step 2:
20 can be fit into 64 3 times, resulting in a remainder of 4.
Write down 3 as next digit of the result. 
Result so far: 3.0
The remainder is 4 after subtracting 60 from 64.
Bring next digit (0) of the dividend behind the 4 and repeat the process: 40 / 20

Let's proceed to step 3:
If we divide 40 by 20, we get 2 and a remainder of 0.
The number 2 becomes the next digit in our result. 
Result so far: 32.0
If we subtract 40 from 40, we get 0.
Include the next digit (6) from the dividend after 0, then repeat: 6 / 20

Let's proceed to step 4:
The number 20 fits into 6 0 times, leaving a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 320.0
If we subtract 0 from 6, we get 6.
Fetch the next digit (2) from the dividend, attach it to 6 and continue: 62 / 20

Going ahead to step 5:
If we divide 62 by 20, we get 3 and a remainder of 2.
The number 3 becomes the next digit in our result. 
Result so far: 3203.0
Subtract 60 from 62 to get 2.
Take the next digit (9) from the dividend and append it to 2, then repeat: 29 / 20

Step 6:
The number 20 fits into 29 1 times, leaving a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 32031.0
Subtracting 20 from 29 leaves us 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 7:
20 goes into 90 4 times with a remainder of 10.
Put 4 as the next digit of the answer. 
Result so far: 32031.4
If we take 80 away from 90, we end up with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On to step 8:
20 can be fit into 100 5 times, resulting in a remainder of 0.
Write down 5 as next digit of the result. 
Result so far: 32031.45
If we subtract 100 from 100, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Advancing to step 9:
20 goes into 0 0 times with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 32031.45
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

On to step 10:
0 divided by 20 is 0 with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 32031.45
Subtracting 0 from 0 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final result is 32031.45 with a remainder of 0.0.