Let's divide 521311 by 15
The aim is to understand the frequency of 15 in 521311.

Going ahead to step 1:
15 goes into 5 0 times with a remainder of 5.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 5, we end up with 5.
Take the next digit (2) from the dividend and append it to 5, then repeat: 52 / 15

Going ahead to step 2:
The number 15 fits into 52 3 times, leaving a remainder of 7.
Put 3 as the next digit of the answer. 
Result so far: 3.0
Deduct 45 from 52 and we're left with 7.
Grab the next digit (1) from the dividend, add it to 7, then carry on: 71 / 15

Moving on to step 3:
15 goes into 71 4 times with a remainder of 11.
Use 4 as the next digit of our solution. 
Result so far: 34.0
Deduct 60 from 71 and we're left with 11.
Fetch the next digit (3) from the dividend, attach it to 11 and continue: 113 / 15

Let's proceed to step 4:
The number 15 fits into 113 7 times, leaving a remainder of 8.
The next digit of our result is 7. 
Result so far: 347.0
Subtracting 105 from 113 leaves us with 8.
Grab the next digit (1) from the dividend, add it to 8, then carry on: 81 / 15

Going ahead to step 5:
When dividing 81 by 15, we get 5 with a remainder of 6.
Write down 5 as next digit of the result. 
Result so far: 3475.0
If we take 75 away from 81, we end up with 6.
Take the next digit (1) from the dividend and append it to 6, then repeat: 61 / 15

Let's proceed to step 6:
61 divided by 15 is 4 with a remainder of 1.
The number 4 becomes the next digit in our result. 
Result so far: 34754.0
Deduct 60 from 61 and we're left with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Going ahead to step 7:
The number 15 fits into 10 0 times, leaving a remainder of 10.
The next digit of our result is 0. 
Result so far: 34754.0
Subtracting 0 from 10 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.

On to step 8:
15 can be fit into 100 6 times, resulting in a remainder of 10.
Record the quotient 6 as the next digit in the result. 
Result so far: 34754.06
Subtract 90 from 100 to get 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 9:
If we divide 100 by 15, we get 6 and a remainder of 10.
Record the quotient 6 as the next digit in the result. 
Result so far: 34754.066
If we subtract 90 from 100, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

The final result is 34754.066 with a remainder of 0.001.