We look at the division of 108491 by 87 
The aim is to understand the frequency of 87 in 108491.

On to step 1:
If we divide 1 by 87, we get 0 and a remainder of 1.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Grab the next digit (0) from the dividend, add it to 1, then carry on: 10 / 87

On to step 2:
When dividing 10 by 87, we get 0 with a remainder of 10.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 10 after subtracting 0 from 10.
Fetch the next digit (8) from the dividend, attach it to 10 and continue: 108 / 87

Moving on to step 3:
87 goes into 108 1 times with a remainder of 21.
Put 1 as the next digit of the answer. 
Result so far: 1.0
If we take 87 away from 108, we end up with 21.
Grab the next digit (4) from the dividend, add it to 21, then carry on: 214 / 87

Moving on to step 4:
If we divide 214 by 87, we get 2 and a remainder of 40.
The number 2 becomes the next digit in our result. 
Result so far: 12.0
Deduct 174 from 214 and we're left with 40.
Append the next digit (9) from the dividend to 40 and continue with: 409 / 87

Advancing to step 5:
87 goes into 409 4 times with a remainder of 61.
Record the quotient 4 as the next digit in the result. 
Result so far: 124.0
If we take 348 away from 409, we end up with 61.
Append the next digit (1) from the dividend to 61 and continue with: 611 / 87

Step 6:
87 goes into 611 7 times with a remainder of 2.
Use 7 as the next digit of our solution. 
Result so far: 1247.0
Deduct 609 from 611 and we're left with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Step 7:
If we divide 20 by 87, we get 0 and a remainder of 20.
The next digit of our result is 0. 
Result so far: 1247.0
Subtracting 0 from 20 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 8:
If we divide 200 by 87, we get 2 and a remainder of 26.
The number 2 becomes the next digit in our result. 
Result so far: 1247.02
If we subtract 174 from 200, we get 26.
Since there are no more digits in the dividend, we add a zero to the remainder making it 260, and continue the process.

On to step 9:
87 goes into 260 2 times with a remainder of 86.
Record the quotient 2 as the next digit in the result. 
Result so far: 1247.022
If we take 174 away from 260, we end up with 86.
Since there are no more digits in the dividend, we add a zero to the remainder making it 860, and continue the process.

The final result is 1247.022 with a remainder of 0.0086.