We look at the division of 664175 by 15 
The aim is to understand the frequency of 15 in 664175.

Advancing to step 1:
When dividing 6 by 15, we get 0 with a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Include the next digit (6) from the dividend after 6, then repeat: 66 / 15

On to step 2:
When dividing 66 by 15, we get 4 with a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 4.0
Deduct 60 from 66 and we're left with 6.
Bring next digit (4) of the dividend behind the 6 and repeat the process: 64 / 15

Going ahead to step 3:
The number 15 fits into 64 4 times, leaving a remainder of 4.
The next digit of our result is 4. 
Result so far: 44.0
Deduct 60 from 64 and we're left with 4.
Take the next digit (1) from the dividend and append it to 4, then repeat: 41 / 15

Going ahead to step 4:
41 divided by 15 is 2 with a remainder of 11.
Put 2 as the next digit of the answer. 
Result so far: 442.0
Subtract 30 from 41 to get 11.
Include the next digit (7) from the dividend after 11, then repeat: 117 / 15

On to step 5:
The number 15 fits into 117 7 times, leaving a remainder of 12.
Record the quotient 7 as the next digit in the result. 
Result so far: 4427.0
If we take 105 away from 117, we end up with 12.
Append the next digit (5) from the dividend to 12 and continue with: 125 / 15

Advancing to step 6:
15 can be fit into 125 8 times, resulting in a remainder of 5.
Record the quotient 8 as the next digit in the result. 
Result so far: 44278.0
Subtracting 120 from 125 leaves us with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

On to step 7:
When dividing 50 by 15, we get 3 with a remainder of 5.
Record the quotient 3 as the next digit in the result. 
Result so far: 44278.3
Deduct 45 from 50 and we're left with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Let's proceed to step 8:
If we divide 50 by 15, we get 3 and a remainder of 5.
The next digit of our result is 3. 
Result so far: 44278.33
Subtract 45 from 50 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Our division results in 44278.33 with a remaining 0.005.