3966 ÷ 25 
The aim is to understand the frequency of 25 in 3966.

Going ahead to step 1:
When dividing 3 by 25, we get 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Include the next digit (9) from the dividend after 3, then repeat: 39 / 25

Step 2:
The number 25 fits into 39 1 times, leaving a remainder of 14.
Write down 1 as next digit of the result. 
Result so far: 1.0
If we take 25 away from 39, we end up with 14.
Fetch the next digit (6) from the dividend, attach it to 14 and continue: 146 / 25

Step 3:
25 can be fit into 146 5 times, resulting in a remainder of 21.
Write down 5 as next digit of the result. 
Result so far: 15.0
Subtracting 125 from 146 leaves us with 21.
Append the next digit (6) from the dividend to 21 and continue with: 216 / 25

Going ahead to step 4:
216 divided by 25 is 8 with a remainder of 16.
The number 8 becomes the next digit in our result. 
Result so far: 158.0
Subtracting 200 from 216 leaves us with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Advancing to step 5:
25 goes into 160 6 times with a remainder of 10.
Write down 6 as next digit of the result. 
Result so far: 158.6
Subtract 150 from 160 to 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.

Let's proceed to step 6:
25 can be fit into 100 4 times, resulting in a remainder of 0.
Write down 4 as next digit of the result. 
Result so far: 158.64
Deduct 100 from 100 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.

Let's proceed to step 7:
If we divide 0 by 25, we get 0 and a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 158.64
Subtracting 0 from 0 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.

Step 8:
25 goes into 0 0 times with a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 158.64
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.

The quotient of the division is 158.64, and the remainder is 0.0.