80713431 ÷ 643 
The aim is to understand the frequency of 643 in 80713431.

Advancing to step 1:
When dividing 8 by 643, we get 0 with a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 8, we end up with 8.
Include the next digit (0) from the dividend after 8, then repeat: 80 / 643

Moving on to step 2:
If we divide 80 by 643, we get 0 and a remainder of 80.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 80 after subtracting 0 from 80.
Take the next digit (7) from the dividend and append it to 80, then repeat: 807 / 643

Let's proceed to step 3:
807 divided by 643 is 1 with a remainder of 164.
Put 1 as the next digit of the answer. 
Result so far: 1.0
If we take 643 away from 807, we end up with 164.
Include the next digit (1) from the dividend after 164, then repeat: 1641 / 643

Step 4:
If we divide 1641 by 643, we get 2 and a remainder of 355.
The number 2 becomes the next digit in our result. 
Result so far: 12.0
Subtract 1286 from 1641 to get 355.
Append the next digit (3) from the dividend to 355 and continue with: 3553 / 643

Going ahead to step 5:
3553 divided by 643 is 5 with a remainder of 338.
Put 5 as the next digit of the answer. 
Result so far: 125.0
Subtracting 3215 from 3553 leaves us with 338.
Bring next digit (4) of the dividend behind the 338 and repeat the process: 3384 / 643

On to step 6:
When dividing 3384 by 643, we get 5 with a remainder of 169.
The number 5 becomes the next digit in our result. 
Result so far: 1255.0
If we subtract 3215 from 3384, we get 169.
Bring next digit (3) of the dividend behind the 169 and repeat the process: 1693 / 643

Advancing to step 7:
1693 divided by 643 is 2 with a remainder of 407.
Put 2 as the next digit of the answer. 
Result so far: 12552.0
Subtracting 1286 from 1693 leaves us with 407.
Grab the next digit (1) from the dividend, add it to 407, then carry on: 4071 / 643

On to step 8:
4071 divided by 643 is 6 with a remainder of 213.
Write down 6 as next digit of the result. 
Result so far: 125526.0
The remainder is 213 after subtracting 3858 from 4071.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2130, and continue the process.

Going ahead to step 9:
If we divide 2130 by 643, we get 3 and a remainder of 201.
Use 3 as the next digit of our solution. 
Result so far: 125526.3
Deduct 1929 from 2130 and we're left with 201.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2010, and continue the process.

Let's proceed to step 10:
If we divide 2010 by 643, we get 3 and a remainder of 81.
Put 3 as the next digit of the answer. 
Result so far: 125526.33
Subtracting 1929 from 2010 leaves us with 81.
Since there are no more digits in the dividend, we add a zero to the remainder making it 810, and continue the process.

The final result is 125526.33 with a remainder of 0.081.