We look at the division of 689428 by 15 
The aim is to understand the frequency of 15 in 689428.

On to step 1:
6 divided by 15 is 0 with a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Bring next digit (8) of the dividend behind the 6 and repeat the process: 68 / 15

On to step 2:
15 goes into 68 4 times with a remainder of 8.
The number 4 becomes the next digit in our result. 
Result so far: 4.0
If we subtract 60 from 68, we get 8.
Include the next digit (9) from the dividend after 8, then repeat: 89 / 15

Let's proceed to step 3:
15 can be fit into 89 5 times, resulting in a remainder of 14.
Record the quotient 5 as the next digit in the result. 
Result so far: 45.0
If we take 75 away from 89, we end up with 14.
Take the next digit (4) from the dividend and append it to 14, then repeat: 144 / 15

Let's proceed to step 4:
15 can be fit into 144 9 times, resulting in a remainder of 9.
Record the quotient 9 as the next digit in the result. 
Result so far: 459.0
Subtract 135 from 144 to get 9.
Grab the next digit (2) from the dividend, add it to 9, then carry on: 92 / 15

Step 5:
When dividing 92 by 15, we get 6 with a remainder of 2.
The number 6 becomes the next digit in our result. 
Result so far: 4596.0
If we subtract 90 from 92, we get 2.
Fetch the next digit (8) from the dividend, attach it to 2 and continue: 28 / 15

Going ahead to step 6:
The number 15 fits into 28 1 times, leaving a remainder of 13.
Record the quotient 1 as the next digit in the result. 
Result so far: 45961.0
If we take 15 away from 28, we end up with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Moving on to step 7:
130 divided by 15 is 8 with a remainder of 10.
Put 8 as the next digit of the answer. 
Result so far: 45961.8
Subtracting 120 from 130 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.

Advancing to step 8:
15 can be fit into 100 6 times, resulting in a remainder of 10.
The next digit of our result is 6. 
Result so far: 45961.86
Subtracting 90 from 100 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.

Step 9:
If we divide 100 by 15, we get 6 and a remainder of 10.
The number 6 becomes the next digit in our result. 
Result so far: 45961.866
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.

Our division results in 45961.866 with a remaining 0.001.