We look at the division of 77939920 by 643 
The aim is to understand the frequency of 643 in 77939920.

Advancing to step 1:
643 goes into 7 0 times with a remainder of 7.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 7, we get 7.
Take the next digit (7) from the dividend and append it to 7, then repeat: 77 / 643

Advancing to step 2:
643 can be fit into 77 0 times, resulting in a remainder of 77.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 77 leaves us with 77.
Grab the next digit (9) from the dividend, add it to 77, then carry on: 779 / 643

Advancing to step 3:
If we divide 779 by 643, we get 1 and a remainder of 136.
Write down 1 as next digit of the result. 
Result so far: 1.0
If we take 643 away from 779, we end up with 136.
Grab the next digit (3) from the dividend, add it to 136, then carry on: 1363 / 643

On to step 4:
643 goes into 1363 2 times with a remainder of 77.
Record the quotient 2 as the next digit in the result. 
Result so far: 12.0
The remainder is 77 after subtracting 1286 from 1363.
Grab the next digit (9) from the dividend, add it to 77, then carry on: 779 / 643

Advancing to step 5:
643 goes into 779 1 times with a remainder of 136.
Put 1 as the next digit of the answer. 
Result so far: 121.0
Subtracting 643 from 779 leaves us with 136.
Include the next digit (9) from the dividend after 136, then repeat: 1369 / 643

Moving on to step 6:
643 goes into 1369 2 times with a remainder of 83.
Put 2 as the next digit of the answer. 
Result so far: 1212.0
Subtract 1286 from 1369 to get 83.
Take the next digit (2) from the dividend and append it to 83, then repeat: 832 / 643

On to step 7:
643 goes into 832 1 times with a remainder of 189.
Record the quotient 1 as the next digit in the result. 
Result so far: 12121.0
If we subtract 643 from 832, we get 189.
Append the next digit (0) from the dividend to 189 and continue with: 1890 / 643

Moving on to step 8:
The number 643 fits into 1890 2 times, leaving a remainder of 604.
Put 2 as the next digit of the answer. 
Result so far: 121212.0
Subtracting 1286 from 1890 leaves us with 604.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6040, and continue the process.

Step 9:
If we divide 6040 by 643, we get 9 and a remainder of 253.
The next digit of our result is 9. 
Result so far: 121212.9
Subtracting 5787 from 6040 leaves us with 253.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2530, and continue the process.

Going ahead to step 10:
643 can be fit into 2530 3 times, resulting in a remainder of 601.
Record the quotient 3 as the next digit in the result. 
Result so far: 121212.93
Subtracting 1929 from 2530 leaves us with 601.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6010, and continue the process.

Step 11:
The number 643 fits into 6010 9 times, leaving a remainder of 223.
Write down 9 as next digit of the result. 
Result so far: 121212.939
If we take 5787 away from 6010, we end up with 223.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2230, and continue the process.

Moving on to step 12:
If we divide 2230 by 643, we get 3 and a remainder of 301.
Record the quotient 3 as the next digit in the result. 
Result so far: 121212.9393
The remainder is 301 after subtracting 1929 from 2230.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3010, and continue the process.

Moving on to step 13:
The number 643 fits into 3010 4 times, leaving a remainder of 438.
Write down 4 as next digit of the result. 
Result so far: 121212.93934
If we take 2572 away from 3010, we end up with 438.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4380, and continue the process.

Moving on to step 14:
The number 643 fits into 4380 6 times, leaving a remainder of 522.
Put 6 as the next digit of the answer. 
Result so far: 121212.939346
The remainder is 522 after subtracting 3858 from 4380.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5220, and continue the process.

On to step 15:
643 goes into 5220 8 times with a remainder of 76.
Use 8 as the next digit of our solution. 
Result so far: 121212.9393468
The remainder is 76 after subtracting 5144 from 5220.
Since there are no more digits in the dividend, we add a zero to the remainder making it 760, and continue the process.

Going ahead to step 16:
If we divide 760 by 643, we get 1 and a remainder of 117.
Use 1 as the next digit of our solution. 
Result so far: 121212.93934681
If we take 643 away from 760, we end up with 117.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1170, and continue the process.

The final outcome is 121212.93934681, with a leftover of 1.17e-07.