We look at the division of 642808 by 51 
The aim is to understand the frequency of 51 in 642808.

Step 1:
The number 51 fits into 6 0 times, leaving a remainder of 6.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Fetch the next digit (4) from the dividend, attach it to 6 and continue: 64 / 51

Moving on to step 2:
The number 51 fits into 64 1 times, leaving a remainder of 13.
Put 1 as the next digit of the answer. 
Result so far: 1.0
Subtracting 51 from 64 leaves us with 13.
Fetch the next digit (2) from the dividend, attach it to 13 and continue: 132 / 51

Going ahead to step 3:
51 goes into 132 2 times with a remainder of 30.
The next digit of our result is 2. 
Result so far: 12.0
Subtract 102 from 132 to get 30.
Grab the next digit (8) from the dividend, add it to 30, then carry on: 308 / 51

Step 4:
If we divide 308 by 51, we get 6 and a remainder of 2.
The next digit of our result is 6. 
Result so far: 126.0
Subtracting 306 from 308 leaves us with 2.
Bring next digit (0) of the dividend behind the 2 and repeat the process: 20 / 51

Let's proceed to step 5:
51 can be fit into 20 0 times, resulting in a remainder of 20.
Record the quotient 0 as the next digit in the result. 
Result so far: 1260.0
Deduct 0 from 20 and we're left with 20.
Bring next digit (8) of the dividend behind the 20 and repeat the process: 208 / 51

On to step 6:
208 divided by 51 is 4 with a remainder of 4.
The next digit of our result is 4. 
Result so far: 12604.0
If we take 204 away from 208, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Let's proceed to step 7:
When dividing 40 by 51, we get 0 with a remainder of 40.
Use 0 as the next digit of our solution. 
Result so far: 12604.0
Subtracting 0 from 40 leaves us with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Advancing to step 8:
51 goes into 400 7 times with a remainder of 43.
Use 7 as the next digit of our solution. 
Result so far: 12604.07
Deduct 357 from 400 and we're left with 43.
Since there are no more digits in the dividend, we add a zero to the remainder making it 430, and continue the process.

Moving on to step 9:
The number 51 fits into 430 8 times, leaving a remainder of 22.
Record the quotient 8 as the next digit in the result. 
Result so far: 12604.078
Deduct 408 from 430 and we're left with 22.
Since there are no more digits in the dividend, we add a zero to the remainder making it 220, and continue the process.

On to step 10:
51 can be fit into 220 4 times, resulting in a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 12604.0784
Subtract 204 from 220 to get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Going ahead to step 11:
If we divide 160 by 51, we get 3 and a remainder of 7.
The next digit of our result is 3. 
Result so far: 12604.07843
Subtract 153 from 160 to get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Let's proceed to step 12:
If we divide 70 by 51, we get 1 and a remainder of 19.
Record the quotient 1 as the next digit in the result. 
Result so far: 12604.078431
If we subtract 51 from 70, we get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Advancing to step 13:
The number 51 fits into 190 3 times, leaving a remainder of 37.
Write down 3 as next digit of the result. 
Result so far: 12604.0784313
If we take 153 away from 190, we end up with 37.
Since there are no more digits in the dividend, we add a zero to the remainder making it 370, and continue the process.

Moving on to step 14:
370 divided by 51 is 7 with a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 12604.07843137
If we take 357 away from 370, we end up with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

After the division, we end up with 12604.07843137 and a remainder of 1.3e-08.