We look at the division of 349878 by 15 
The aim is to understand the frequency of 15 in 349878.

Step 1:
15 can be fit into 3 0 times, resulting in a remainder of 3.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Fetch the next digit (4) from the dividend, attach it to 3 and continue: 34 / 15

Moving on to step 2:
If we divide 34 by 15, we get 2 and a remainder of 4.
Write down 2 as next digit of the result. 
Result so far: 2.0
If we subtract 30 from 34, we get 4.
Take the next digit (9) from the dividend and append it to 4, then repeat: 49 / 15

Step 3:
The number 15 fits into 49 3 times, leaving a remainder of 4.
Use 3 as the next digit of our solution. 
Result so far: 23.0
Subtract 45 from 49 to get 4.
Include the next digit (8) from the dividend after 4, then repeat: 48 / 15

Advancing to step 4:
48 divided by 15 is 3 with a remainder of 3.
The next digit of our result is 3. 
Result so far: 233.0
The remainder is 3 after subtracting 45 from 48.
Bring next digit (7) of the dividend behind the 3 and repeat the process: 37 / 15

Step 5:
37 divided by 15 is 2 with a remainder of 7.
The next digit of our result is 2. 
Result so far: 2332.0
Subtract 30 from 37 to get 7.
Grab the next digit (8) from the dividend, add it to 7, then carry on: 78 / 15

Step 6:
If we divide 78 by 15, we get 5 and a remainder of 3.
The number 5 becomes the next digit in our result. 
Result so far: 23325.0
If we subtract 75 from 78, we get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Let's proceed to step 7:
When dividing 30 by 15, we get 2 with a remainder of 0.
The number 2 becomes the next digit in our result. 
Result so far: 23325.2
Deduct 30 from 30 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.

Going ahead to step 8:
0 divided by 15 is 0 with a remainder of 0.
The next digit of our result is 0. 
Result so far: 23325.2
Subtract 0 from 0 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.

Moving on 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: 23325.2
If we take 0 away from 0, we end up 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 23325.2 and a remainder of 0.0.