We look at the division of 309886 by 75 
The aim is to understand the frequency of 75 in 309886.

On to step 1:
3 divided by 75 is 0 with a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 3, we get 3.
Append the next digit (0) from the dividend to 3 and continue with: 30 / 75

Let's proceed to step 2:
30 divided by 75 is 0 with a remainder of 30.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 30 and we're left with 30.
Fetch the next digit (9) from the dividend, attach it to 30 and continue: 309 / 75

Going ahead to step 3:
75 can be fit into 309 4 times, resulting in a remainder of 9.
Use 4 as the next digit of our solution. 
Result so far: 4.0
The remainder is 9 after subtracting 300 from 309.
Grab the next digit (8) from the dividend, add it to 9, then carry on: 98 / 75

On to step 4:
98 divided by 75 is 1 with a remainder of 23.
Write down 1 as next digit of the result. 
Result so far: 41.0
If we subtract 75 from 98, we get 23.
Include the next digit (8) from the dividend after 23, then repeat: 238 / 75

Going ahead to step 5:
If we divide 238 by 75, we get 3 and a remainder of 13.
Record the quotient 3 as the next digit in the result. 
Result so far: 413.0
Subtracting 225 from 238 leaves us with 13.
Append the next digit (6) from the dividend to 13 and continue with: 136 / 75

Moving on to step 6:
75 can be fit into 136 1 times, resulting in a remainder of 61.
The number 1 becomes the next digit in our result. 
Result so far: 4131.0
Deduct 75 from 136 and we're left with 61.
Since there are no more digits in the dividend, we add a zero to the remainder making it 610, and continue the process.

On to step 7:
The number 75 fits into 610 8 times, leaving a remainder of 10.
The next digit of our result is 8. 
Result so far: 4131.8
If we subtract 600 from 610, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On to step 8:
75 can be fit into 100 1 times, resulting in a remainder of 25.
Put 1 as the next digit of the answer. 
Result so far: 4131.81
The remainder is 25 after subtracting 75 from 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

On to step 9:
250 divided by 75 is 3 with a remainder of 25.
Write down 3 as next digit of the result. 
Result so far: 4131.813
If we subtract 225 from 250, we get 25.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

Going ahead to step 10:
The number 75 fits into 250 3 times, leaving a remainder of 25.
The number 3 becomes the next digit in our result. 
Result so far: 4131.8133
The remainder is 25 after subtracting 225 from 250.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

After the division, we end up with 4131.8133 and a remainder of 0.00025.