We're dividing 139951 by 91 
The aim is to understand the frequency of 91 in 139951.

On to step 1:
91 goes into 1 0 times with a remainder of 1.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 1 leaves us with 1.
Take the next digit (3) from the dividend and append it to 1, then repeat: 13 / 91

Moving on to step 2:
13 divided by 91 is 0 with a remainder of 13.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 13, we end up with 13.
Include the next digit (9) from the dividend after 13, then repeat: 139 / 91

Going ahead to step 3:
139 divided by 91 is 1 with a remainder of 48.
Write down 1 as next digit of the result. 
Result so far: 1.0
If we subtract 91 from 139, we get 48.
Bring next digit (9) of the dividend behind the 48 and repeat the process: 489 / 91

On to step 4:
When dividing 489 by 91, we get 5 with a remainder of 34.
Use 5 as the next digit of our solution. 
Result so far: 15.0
Deduct 455 from 489 and we're left with 34.
Include the next digit (5) from the dividend after 34, then repeat: 345 / 91

Let's proceed to step 5:
When dividing 345 by 91, we get 3 with a remainder of 72.
The number 3 becomes the next digit in our result. 
Result so far: 153.0
If we take 273 away from 345, we end up with 72.
Bring next digit (1) of the dividend behind the 72 and repeat the process: 721 / 91

Going ahead to step 6:
If we divide 721 by 91, we get 7 and a remainder of 84.
Record the quotient 7 as the next digit in the result. 
Result so far: 1537.0
The remainder is 84 after subtracting 637 from 721.
Since there are no more digits in the dividend, we add a zero to the remainder making it 840, and continue the process.

On to step 7:
91 goes into 840 9 times with a remainder of 21.
Put 9 as the next digit of the answer. 
Result so far: 1537.9
If we take 819 away from 840, we end up with 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Going ahead to step 8:
When dividing 210 by 91, we get 2 with a remainder of 28.
The next digit of our result is 2. 
Result so far: 1537.92
The remainder is 28 after subtracting 182 from 210.
Since there are no more digits in the dividend, we add a zero to the remainder making it 280, and continue the process.

Advancing to step 9:
If we divide 280 by 91, we get 3 and a remainder of 7.
The number 3 becomes the next digit in our result. 
Result so far: 1537.923
The remainder is 7 after subtracting 273 from 280.
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 10:
If we divide 70 by 91, we get 0 and a remainder of 70.
Record the quotient 0 as the next digit in the result. 
Result so far: 1537.923
Deduct 0 from 70 and we're left with 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 700, and continue the process.

Moving on to step 11:
91 goes into 700 7 times with a remainder of 63.
The number 7 becomes the next digit in our result. 
Result so far: 1537.92307
If we subtract 637 from 700, we get 63.
Since there are no more digits in the dividend, we add a zero to the remainder making it 630, and continue the process.

Going ahead to step 12:
91 can be fit into 630 6 times, resulting in a remainder of 84.
Record the quotient 6 as the next digit in the result. 
Result so far: 1537.923076
Subtracting 546 from 630 leaves us with 84.
Since there are no more digits in the dividend, we add a zero to the remainder making it 840, and continue the process.

Step 13:
When dividing 840 by 91, we get 9 with a remainder of 21.
The number 9 becomes the next digit in our result. 
Result so far: 1537.9230769
Subtract 819 from 840 to get 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Advancing to step 14:
210 divided by 91 is 2 with a remainder of 28.
The number 2 becomes the next digit in our result. 
Result so far: 1537.92307692
The remainder is 28 after subtracting 182 from 210.
Since there are no more digits in the dividend, we add a zero to the remainder making it 280, and continue the process.

Our division results in 1537.92307692 with a remaining 2.8e-08.