Let's divide 138921 by 39
The aim is to understand the frequency of 39 in 138921.

Step 1:
39 goes into 1 0 times with a remainder of 1.
Record the quotient 0 as the next digit in the result. 
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 / 39

Moving on to step 2:
The number 39 fits into 13 0 times, leaving a remainder of 13.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we subtract 0 from 13, we get 13.
Grab the next digit (8) from the dividend, add it to 13, then carry on: 138 / 39

On to step 3:
39 can be fit into 138 3 times, resulting in a remainder of 21.
The next digit of our result is 3. 
Result so far: 3.0
Subtracting 117 from 138 leaves us with 21.
Grab the next digit (9) from the dividend, add it to 21, then carry on: 219 / 39

Going ahead to step 4:
219 divided by 39 is 5 with a remainder of 24.
Record the quotient 5 as the next digit in the result. 
Result so far: 35.0
If we take 195 away from 219, we end up with 24.
Include the next digit (2) from the dividend after 24, then repeat: 242 / 39

Let's proceed to step 5:
The number 39 fits into 242 6 times, leaving a remainder of 8.
Write down 6 as next digit of the result. 
Result so far: 356.0
Deduct 234 from 242 and we're left with 8.
Append the next digit (1) from the dividend to 8 and continue with: 81 / 39

Moving on to step 6:
If we divide 81 by 39, we get 2 and a remainder of 3.
Use 2 as the next digit of our solution. 
Result so far: 3562.0
Subtracting 78 from 81 leaves us with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Advancing to step 7:
When dividing 30 by 39, we get 0 with a remainder of 30.
The next digit of our result is 0. 
Result so far: 3562.0
If we subtract 0 from 30, we get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Advancing to step 8:
When dividing 300 by 39, we get 7 with a remainder of 27.
Record the quotient 7 as the next digit in the result. 
Result so far: 3562.07
If we take 273 away from 300, we end up with 27.
Since there are no more digits in the dividend, we add a zero to the remainder making it 270, and continue the process.

Moving on to step 9:
39 can be fit into 270 6 times, resulting in a remainder of 36.
Put 6 as the next digit of the answer. 
Result so far: 3562.076
Subtracting 234 from 270 leaves us with 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Moving on to step 10:
39 can be fit into 360 9 times, resulting in a remainder of 9.
The next digit of our result is 9. 
Result so far: 3562.0769
Deduct 351 from 360 and we're left with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

On to step 11:
When dividing 90 by 39, we get 2 with a remainder of 12.
Write down 2 as next digit of the result. 
Result so far: 3562.07692
Subtracting 78 from 90 leaves us 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.

Going ahead to step 12:
39 goes into 120 3 times with a remainder of 3.
Use 3 as the next digit of our solution. 
Result so far: 3562.076923
Subtract 117 from 120 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Let's proceed to step 13:
39 goes into 30 0 times with a remainder of 30.
The next digit of our result is 0. 
Result so far: 3562.076923
If we take 0 away from 30, we end up with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

On to step 14:
39 can be fit into 300 7 times, resulting in a remainder of 27.
Put 7 as the next digit of the answer. 
Result so far: 3562.07692307
If we take 273 away from 300, we end up with 27.
Since there are no more digits in the dividend, we add a zero to the remainder making it 270, and continue the process.

After the division, we end up with 3562.07692307 and a remainder of 2.7e-08.