Let's divide 399419 by 15
The aim is to understand the frequency of 15 in 399419.

Advancing to step 1:
3 divided by 15 is 0 with a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 3, we end up with 3.
Fetch the next digit (9) from the dividend, attach it to 3 and continue: 39 / 15

On to step 2:
If we divide 39 by 15, we get 2 and a remainder of 9.
The number 2 becomes the next digit in our result. 
Result so far: 2.0
Subtract 30 from 39 to get 9.
Grab the next digit (9) from the dividend, add it to 9, then carry on: 99 / 15

Going ahead to step 3:
When dividing 99 by 15, we get 6 with a remainder of 9.
Put 6 as the next digit of the answer. 
Result so far: 26.0
Subtract 90 from 99 to get 9.
Include the next digit (4) from the dividend after 9, then repeat: 94 / 15

Moving on to step 4:
If we divide 94 by 15, we get 6 and a remainder of 4.
Use 6 as the next digit of our solution. 
Result so far: 266.0
Subtract 90 from 94 to get 4.
Fetch the next digit (1) from the dividend, attach it to 4 and continue: 41 / 15

Going ahead to step 5:
The number 15 fits into 41 2 times, leaving a remainder of 11.
Put 2 as the next digit of the answer. 
Result so far: 2662.0
Deduct 30 from 41 and we're left with 11.
Append the next digit (9) from the dividend to 11 and continue with: 119 / 15

Step 6:
If we divide 119 by 15, we get 7 and a remainder of 14.
Use 7 as the next digit of our solution. 
Result so far: 26627.0
If we subtract 105 from 119, we get 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Advancing to step 7:
140 divided by 15 is 9 with a remainder of 5.
The next digit of our result is 9. 
Result so far: 26627.9
If we take 135 away from 140, we end up 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.

Moving on to step 8:
When dividing 50 by 15, we get 3 with a remainder of 5.
The number 3 becomes the next digit in our result. 
Result so far: 26627.93
If we subtract 45 from 50, we 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.

Going ahead to step 9:
The number 15 fits into 50 3 times, leaving a remainder of 5.
The number 3 becomes the next digit in our result. 
Result so far: 26627.933
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.

The quotient of the division is 26627.933, and the remainder is 0.0005.