We look at the division of 638680 by 86 
The aim is to understand the frequency of 86 in 638680.

On to step 1:
If we divide 6 by 86, we get 0 and a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Grab the next digit (3) from the dividend, add it to 6, then carry on: 63 / 86

On to step 2:
86 goes into 63 0 times with a remainder of 63.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 63 after subtracting 0 from 63.
Include the next digit (8) from the dividend after 63, then repeat: 638 / 86

On to step 3:
The number 86 fits into 638 7 times, leaving a remainder of 36.
Record the quotient 7 as the next digit in the result. 
Result so far: 7.0
Subtracting 602 from 638 leaves us with 36.
Append the next digit (6) from the dividend to 36 and continue with: 366 / 86

Advancing to step 4:
When dividing 366 by 86, we get 4 with a remainder of 22.
Use 4 as the next digit of our solution. 
Result so far: 74.0
Subtract 344 from 366 to get 22.
Append the next digit (8) from the dividend to 22 and continue with: 228 / 86

Going ahead to step 5:
If we divide 228 by 86, we get 2 and a remainder of 56.
Put 2 as the next digit of the answer. 
Result so far: 742.0
Subtracting 172 from 228 leaves us with 56.
Append the next digit (0) from the dividend to 56 and continue with: 560 / 86

Step 6:
86 goes into 560 6 times with a remainder of 44.
Use 6 as the next digit of our solution. 
Result so far: 7426.0
Subtract 516 from 560 to get 44.
Since there are no more digits in the dividend, we add a zero to the remainder making it 440, and continue the process.

Advancing to step 7:
86 goes into 440 5 times with a remainder of 10.
The next digit of our result is 5. 
Result so far: 7426.5
Subtracting 430 from 440 leaves us 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.

Moving on to step 8:
86 goes into 100 1 times with a remainder of 14.
Use 1 as the next digit of our solution. 
Result so far: 7426.51
Subtract 86 from 100 to get 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Going ahead to step 9:
The number 86 fits into 140 1 times, leaving a remainder of 54.
The next digit of our result is 1. 
Result so far: 7426.511
Deduct 86 from 140 and we're left with 54.
Since there are no more digits in the dividend, we add a zero to the remainder making it 540, and continue the process.

The quotient of the division is 7426.511, and the remainder is 0.0054.