We're dividing 13512578 by 15 
The aim is to understand the frequency of 15 in 13512578.

Let's proceed to step 1:
When dividing 1 by 15, we get 0 with a remainder of 1.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 1 to get 1.
Grab the next digit (3) from the dividend, add it to 1, then carry on: 13 / 15

Advancing to step 2:
The number 15 fits into 13 0 times, leaving a remainder of 13.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 13 and we're left with 13.
Include the next digit (5) from the dividend after 13, then repeat: 135 / 15

Step 3:
When dividing 135 by 15, we get 9 with a remainder of 0.
Write down 9 as next digit of the result. 
Result so far: 9.0
The remainder is 0 after subtracting 135 from 135.
Include the next digit (1) from the dividend after 0, then repeat: 1 / 15

Advancing to step 4:
When dividing 1 by 15, we get 0 with a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 90.0
If we take 0 away from 1, we end up with 1.
Take the next digit (2) from the dividend and append it to 1, then repeat: 12 / 15

Advancing to step 5:
The number 15 fits into 12 0 times, leaving a remainder of 12.
Write down 0 as next digit of the result. 
Result so far: 900.0
If we subtract 0 from 12, we get 12.
Include the next digit (5) from the dividend after 12, then repeat: 125 / 15

Let's proceed to step 6:
15 can be fit into 125 8 times, resulting in a remainder of 5.
Put 8 as the next digit of the answer. 
Result so far: 9008.0
If we subtract 120 from 125, we get 5.
Take the next digit (7) from the dividend and append it to 5, then repeat: 57 / 15

Step 7:
15 can be fit into 57 3 times, resulting in a remainder of 12.
The number 3 becomes the next digit in our result. 
Result so far: 90083.0
Subtracting 45 from 57 leaves us with 12.
Take the next digit (8) from the dividend and append it to 12, then repeat: 128 / 15

Moving on to step 8:
When dividing 128 by 15, we get 8 with a remainder of 8.
The number 8 becomes the next digit in our result. 
Result so far: 900838.0
Deduct 120 from 128 and we're left with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Let's proceed to step 9:
80 divided by 15 is 5 with a remainder of 5.
Write down 5 as next digit of the result. 
Result so far: 900838.5
The remainder is 5 after subtracting 75 from 80.
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 10:
15 goes into 50 3 times with a remainder of 5.
Put 3 as the next digit of the answer. 
Result so far: 900838.53
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.

Step 11:
When dividing 50 by 15, we get 3 with a remainder of 5.
The next digit of our result is 3. 
Result so far: 900838.533
The remainder is 5 after subtracting 45 from 50.
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 900838.533 with a remaining 0.0005.