573799 divided by 15 
The aim is to understand the frequency of 15 in 573799.

Step 1:
The number 15 fits into 5 0 times, leaving a remainder of 5.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 5 to get 5.
Grab the next digit (7) from the dividend, add it to 5, then carry on: 57 / 15

On to step 2:
15 can be fit into 57 3 times, resulting in a remainder of 12.
Use 3 as the next digit of our solution. 
Result so far: 3.0
The remainder is 12 after subtracting 45 from 57.
Append the next digit (3) from the dividend to 12 and continue with: 123 / 15

On to step 3:
15 goes into 123 8 times with a remainder of 3.
Record the quotient 8 as the next digit in the result. 
Result so far: 38.0
Subtracting 120 from 123 leaves us with 3.
Append the next digit (7) from the dividend to 3 and continue with: 37 / 15

Moving on to step 4:
If we divide 37 by 15, we get 2 and a remainder of 7.
Record the quotient 2 as the next digit in the result. 
Result so far: 382.0
Subtract 30 from 37 to get 7.
Include the next digit (9) from the dividend after 7, then repeat: 79 / 15

Moving on to step 5:
15 can be fit into 79 5 times, resulting in a remainder of 4.
The next digit of our result is 5. 
Result so far: 3825.0
Deduct 75 from 79 and we're left with 4.
Grab the next digit (9) from the dividend, add it to 4, then carry on: 49 / 15

Going ahead to step 6:
49 divided by 15 is 3 with a remainder of 4.
The number 3 becomes the next digit in our result. 
Result so far: 38253.0
Subtract 45 from 49 to get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 7:
40 divided by 15 is 2 with a remainder of 10.
Write down 2 as next digit of the result. 
Result so far: 38253.2
Subtracting 30 from 40 leaves us 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.

Going ahead to step 8:
When dividing 100 by 15, we get 6 with a remainder of 10.
Record the quotient 6 as the next digit in the result. 
Result so far: 38253.26
The remainder is 10 after subtracting 90 from 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Moving on to step 9:
100 divided by 15 is 6 with a remainder of 10.
Use 6 as the next digit of our solution. 
Result so far: 38253.266
Deduct 90 from 100 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.

The final outcome is 38253.266, with a leftover of 0.001.