20851 ÷ 91 
The aim is to understand the frequency of 91 in 20851.

Step 1:
2 divided by 91 is 0 with a remainder of 2.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 2 to get 2.
Bring next digit (0) of the dividend behind the 2 and repeat the process: 20 / 91

Moving on to step 2:
20 divided by 91 is 0 with a remainder of 20.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 20 leaves us with 20.
Fetch the next digit (8) from the dividend, attach it to 20 and continue: 208 / 91

Advancing to step 3:
When dividing 208 by 91, we get 2 with a remainder of 26.
Record the quotient 2 as the next digit in the result. 
Result so far: 2.0
Subtract 182 from 208 to get 26.
Bring next digit (5) of the dividend behind the 26 and repeat the process: 265 / 91

Going ahead to step 4:
91 goes into 265 2 times with a remainder of 83.
Write down 2 as next digit of the result. 
Result so far: 22.0
Subtract 182 from 265 to get 83.
Bring next digit (1) of the dividend behind the 83 and repeat the process: 831 / 91

Step 5:
When dividing 831 by 91, we get 9 with a remainder of 12.
Record the quotient 9 as the next digit in the result. 
Result so far: 229.0
If we subtract 819 from 831, we get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 6:
120 divided by 91 is 1 with a remainder of 29.
The number 1 becomes the next digit in our result. 
Result so far: 229.1
If we subtract 91 from 120, we get 29.
Since there are no more digits in the dividend, we add a zero to the remainder making it 290, and continue the process.

On to step 7:
If we divide 290 by 91, we get 3 and a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 229.13
The remainder is 17 after subtracting 273 from 290.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Going ahead to step 8:
91 can be fit into 170 1 times, resulting in a remainder of 79.
Use 1 as the next digit of our solution. 
Result so far: 229.131
The remainder is 79 after subtracting 91 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 790, and continue the process.

Going ahead to step 9:
91 can be fit into 790 8 times, resulting in a remainder of 62.
Record the quotient 8 as the next digit in the result. 
Result so far: 229.1318
The remainder is 62 after subtracting 728 from 790.
Since there are no more digits in the dividend, we add a zero to the remainder making it 620, and continue the process.

Advancing to step 10:
The number 91 fits into 620 6 times, leaving a remainder of 74.
Write down 6 as next digit of the result. 
Result so far: 229.13186
Deduct 546 from 620 and we're left with 74.
Since there are no more digits in the dividend, we add a zero to the remainder making it 740, and continue the process.

Advancing to step 11:
The number 91 fits into 740 8 times, leaving a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 229.131868
If we take 728 away from 740, we end up with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 12:
91 goes into 120 1 times with a remainder of 29.
The number 1 becomes the next digit in our result. 
Result so far: 229.1318681
Subtracting 91 from 120 leaves us with 29.
Since there are no more digits in the dividend, we add a zero to the remainder making it 290, and continue the process.

Let's proceed to step 13:
When dividing 290 by 91, we get 3 with a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 229.13186813
If we subtract 273 from 290, we get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

The final result is 229.13186813 with a remainder of 1.7e-08.