399958 divided by 39 
The aim is to understand the frequency of 39 in 399958.

Let's proceed to step 1:
The number 39 fits into 3 0 times, leaving a remainder of 3.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 39

Going ahead to step 2:
If we divide 39 by 39, we get 1 and a remainder of 0.
Put 1 as the next digit of the answer. 
Result so far: 1.0
The remainder is 0 after subtracting 39 from 39.
Bring next digit (9) of the dividend behind the 0 and repeat the process: 9 / 39

Step 3:
When dividing 9 by 39, we get 0 with a remainder of 9.
The number 0 becomes the next digit in our result. 
Result so far: 10.0
The remainder is 9 after subtracting 0 from 9.
Include the next digit (9) from the dividend after 9, then repeat: 99 / 39

On to step 4:
99 divided by 39 is 2 with a remainder of 21.
Record the quotient 2 as the next digit in the result. 
Result so far: 102.0
Subtracting 78 from 99 leaves us with 21.
Include the next digit (5) from the dividend after 21, then repeat: 215 / 39

Advancing to step 5:
39 goes into 215 5 times with a remainder of 20.
Record the quotient 5 as the next digit in the result. 
Result so far: 1025.0
If we subtract 195 from 215, we get 20.
Grab the next digit (8) from the dividend, add it to 20, then carry on: 208 / 39

Moving on to step 6:
If we divide 208 by 39, we get 5 and a remainder of 13.
The next digit of our result is 5. 
Result so far: 10255.0
The remainder is 13 after subtracting 195 from 208.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Step 7:
If we divide 130 by 39, we get 3 and a remainder of 13.
The number 3 becomes the next digit in our result. 
Result so far: 10255.3
Subtracting 117 from 130 leaves us with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 8:
39 can be fit into 130 3 times, resulting in a remainder of 13.
Write down 3 as next digit of the result. 
Result so far: 10255.33
If we subtract 117 from 130, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Our division results in 10255.33 with a remaining 0.013.