393999 ÷ 25 
The aim is to understand the frequency of 25 in 393999.

Let's proceed to step 1:
3 divided by 25 is 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 3, we end up with 3.
Grab the next digit (9) from the dividend, add it to 3, then carry on: 39 / 25

Moving on to step 2:
The number 25 fits into 39 1 times, leaving a remainder of 14.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Deduct 25 from 39 and we're left with 14.
Include the next digit (3) from the dividend after 14, then repeat: 143 / 25

Step 3:
25 goes into 143 5 times with a remainder of 18.
The next digit of our result is 5. 
Result so far: 15.0
Deduct 125 from 143 and we're left with 18.
Append the next digit (9) from the dividend to 18 and continue with: 189 / 25

Step 4:
25 goes into 189 7 times with a remainder of 14.
The number 7 becomes the next digit in our result. 
Result so far: 157.0
If we subtract 175 from 189, we get 14.
Bring next digit (9) of the dividend behind the 14 and repeat the process: 149 / 25

Going ahead to step 5:
The number 25 fits into 149 5 times, leaving a remainder of 24.
Use 5 as the next digit of our solution. 
Result so far: 1575.0
If we subtract 125 from 149, we get 24.
Append the next digit (9) from the dividend to 24 and continue with: 249 / 25

Step 6:
25 can be fit into 249 9 times, resulting in a remainder of 24.
Record the quotient 9 as the next digit in the result. 
Result so far: 15759.0
Subtract 225 from 249 to get 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

Let's proceed to step 7:
25 goes into 240 9 times with a remainder of 15.
Record the quotient 9 as the next digit in the result. 
Result so far: 15759.9
Subtracting 225 from 240 leaves us with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Let's proceed to step 8:
When dividing 150 by 25, we get 6 with a remainder of 0.
Write down 6 as next digit of the result. 
Result so far: 15759.96
Subtracting 150 from 150 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Advancing to step 9:
0 divided by 25 is 0 with a remainder of 0.
The next digit of our result is 0. 
Result so far: 15759.96
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

On to step 10:
The number 25 fits into 0 0 times, leaving a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 15759.96
Deduct 0 from 0 and we're left with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final outcome is 15759.96, with a leftover of 0.0.