We look at the division of 23891740 by 399 
The aim is to understand the frequency of 399 in 23891740.

Step 1:
399 can be fit into 2 0 times, resulting in a remainder of 2.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 2, we get 2.
Grab the next digit (3) from the dividend, add it to 2, then carry on: 23 / 399

Advancing to step 2:
If we divide 23 by 399, we get 0 and a remainder of 23.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 23 and we're left with 23.
Grab the next digit (8) from the dividend, add it to 23, then carry on: 238 / 399

Advancing to step 3:
238 divided by 399 is 0 with a remainder of 238.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 238 after subtracting 0 from 238.
Fetch the next digit (9) from the dividend, attach it to 238 and continue: 2389 / 399

On to step 4:
The number 399 fits into 2389 5 times, leaving a remainder of 394.
Put 5 as the next digit of the answer. 
Result so far: 5.0
Deduct 1995 from 2389 and we're left with 394.
Fetch the next digit (1) from the dividend, attach it to 394 and continue: 3941 / 399

Step 5:
399 goes into 3941 9 times with a remainder of 350.
The number 9 becomes the next digit in our result. 
Result so far: 59.0
Subtracting 3591 from 3941 leaves us with 350.
Grab the next digit (7) from the dividend, add it to 350, then carry on: 3507 / 399

Step 6:
When dividing 3507 by 399, we get 8 with a remainder of 315.
Put 8 as the next digit of the answer. 
Result so far: 598.0
Deduct 3192 from 3507 and we're left with 315.
Fetch the next digit (4) from the dividend, attach it to 315 and continue: 3154 / 399

Advancing to step 7:
The number 399 fits into 3154 7 times, leaving a remainder of 361.
Write down 7 as next digit of the result. 
Result so far: 5987.0
If we subtract 2793 from 3154, we get 361.
Fetch the next digit (0) from the dividend, attach it to 361 and continue: 3610 / 399

Step 8:
When dividing 3610 by 399, we get 9 with a remainder of 19.
The number 9 becomes the next digit in our result. 
Result so far: 59879.0
Deduct 3591 from 3610 and we're left with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Advancing to step 9:
190 divided by 399 is 0 with a remainder of 190.
Put 0 as the next digit of the answer. 
Result so far: 59879.0
If we take 0 away from 190, we end up with 190.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1900, and continue the process.

Let's proceed to step 10:
399 can be fit into 1900 4 times, resulting in a remainder of 304.
Record the quotient 4 as the next digit in the result. 
Result so far: 59879.04
If we subtract 1596 from 1900, we get 304.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3040, and continue the process.

Step 11:
399 can be fit into 3040 7 times, resulting in a remainder of 247.
Put 7 as the next digit of the answer. 
Result so far: 59879.047
The remainder is 247 after subtracting 2793 from 3040.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2470, and continue the process.

Moving on to step 12:
The number 399 fits into 2470 6 times, leaving a remainder of 76.
Put 6 as the next digit of the answer. 
Result so far: 59879.0476
Subtract 2394 from 2470 to get 76.
Since there are no more digits in the dividend, we add a zero to the remainder making it 760, and continue the process.

Let's proceed to step 13:
When dividing 760 by 399, we get 1 with a remainder of 361.
Use 1 as the next digit of our solution. 
Result so far: 59879.04761
If we subtract 399 from 760, we get 361.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3610, and continue the process.

On to step 14:
If we divide 3610 by 399, we get 9 and a remainder of 19.
The next digit of our result is 9. 
Result so far: 59879.047619
Deduct 3591 from 3610 and we're left with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Going ahead to step 15:
399 goes into 190 0 times with a remainder of 190.
Use 0 as the next digit of our solution. 
Result so far: 59879.047619
If we subtract 0 from 190, we get 190.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1900, and continue the process.

Advancing to step 16:
399 can be fit into 1900 4 times, resulting in a remainder of 304.
Record the quotient 4 as the next digit in the result. 
Result so far: 59879.04761904
Subtracting 1596 from 1900 leaves us with 304.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3040, and continue the process.

The final result is 59879.04761904 with a remainder of 3.04e-07.