583966 ÷ 15 
The aim is to understand the frequency of 15 in 583966.

Advancing to step 1:
When dividing 5 by 15, we get 0 with a remainder of 5.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 5 leaves us with 5.
Include the next digit (8) from the dividend after 5, then repeat: 58 / 15

On to step 2:
15 can be fit into 58 3 times, resulting in a remainder of 13.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Subtracting 45 from 58 leaves us with 13.
Grab the next digit (3) from the dividend, add it to 13, then carry on: 133 / 15

Going ahead to step 3:
15 can be fit into 133 8 times, resulting in a remainder of 13.
The number 8 becomes the next digit in our result. 
Result so far: 38.0
Subtracting 120 from 133 leaves us with 13.
Fetch the next digit (9) from the dividend, attach it to 13 and continue: 139 / 15

Moving on to step 4:
15 can be fit into 139 9 times, resulting in a remainder of 4.
Put 9 as the next digit of the answer. 
Result so far: 389.0
If we take 135 away from 139, we end up with 4.
Append the next digit (6) from the dividend to 4 and continue with: 46 / 15

Advancing to step 5:
The number 15 fits into 46 3 times, leaving a remainder of 1.
The number 3 becomes the next digit in our result. 
Result so far: 3893.0
Subtract 45 from 46 to get 1.
Grab the next digit (6) from the dividend, add it to 1, then carry on: 16 / 15

Let's proceed to step 6:
The number 15 fits into 16 1 times, leaving a remainder of 1.
The next digit of our result is 1. 
Result so far: 38931.0
Subtract 15 from 16 to get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Let's proceed to step 7:
10 divided by 15 is 0 with a remainder of 10.
Write down 0 as next digit of the result. 
Result so far: 38931.0
Deduct 0 from 10 and we're left with 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 8:
When dividing 100 by 15, we get 6 with a remainder of 10.
The number 6 becomes the next digit in our result. 
Result so far: 38931.06
If we subtract 90 from 100, we 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.

Step 9:
When dividing 100 by 15, we get 6 with a remainder of 10.
Put 6 as the next digit of the answer. 
Result so far: 38931.066
If we subtract 90 from 100, we 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.

After the division, we end up with 38931.066 and a remainder of 0.001.