255921 ÷ 15 
The aim is to understand the frequency of 15 in 255921.

Step 1:
15 can be fit into 2 0 times, resulting in a remainder of 2.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 2 to get 2.
Take the next digit (5) from the dividend and append it to 2, then repeat: 25 / 15

Going ahead to step 2:
If we divide 25 by 15, we get 1 and a remainder of 10.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Subtract 15 from 25 to get 10.
Take the next digit (5) from the dividend and append it to 10, then repeat: 105 / 15

Let's proceed to step 3:
15 goes into 105 7 times with a remainder of 0.
Use 7 as the next digit of our solution. 
Result so far: 17.0
If we subtract 105 from 105, we get 0.
Take the next digit (9) from the dividend and append it to 0, then repeat: 9 / 15

Let's proceed to step 4:
15 goes into 9 0 times with a remainder of 9.
Use 0 as the next digit of our solution. 
Result so far: 170.0
If we take 0 away from 9, we end up with 9.
Grab the next digit (2) from the dividend, add it to 9, then carry on: 92 / 15

On to step 5:
The number 15 fits into 92 6 times, leaving a remainder of 2.
The number 6 becomes the next digit in our result. 
Result so far: 1706.0
If we subtract 90 from 92, we get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 15

Moving on to step 6:
The number 15 fits into 21 1 times, leaving a remainder of 6.
Put 1 as the next digit of the answer. 
Result so far: 17061.0
Subtracting 15 from 21 leaves us with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 7:
If we divide 60 by 15, we get 4 and a remainder of 0.
Record the quotient 4 as the next digit in the result. 
Result so far: 17061.4
Subtract 60 from 60 to get 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:
15 can be fit into 0 0 times, resulting in a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 17061.4
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.

Advancing to step 9:
If we divide 0 by 15, we get 0 and a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 17061.4
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.

After the division, we end up with 17061.4 and a remainder of 0.0.