We look at the division of 877535 by 13 
The aim is to understand the frequency of 13 in 877535.

On to step 1:
If we divide 8 by 13, we get 0 and a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 8 to get 8.
Grab the next digit (7) from the dividend, add it to 8, then carry on: 87 / 13

Moving on to step 2:
13 goes into 87 6 times with a remainder of 9.
Use 6 as the next digit of our solution. 
Result so far: 6.0
If we take 78 away from 87, we end up with 9.
Fetch the next digit (7) from the dividend, attach it to 9 and continue: 97 / 13

Moving on to step 3:
13 goes into 97 7 times with a remainder of 6.
Put 7 as the next digit of the answer. 
Result so far: 67.0
The remainder is 6 after subtracting 91 from 97.
Take the next digit (5) from the dividend and append it to 6, then repeat: 65 / 13

Let's proceed to step 4:
65 divided by 13 is 5 with a remainder of 0.
The next digit of our result is 5. 
Result so far: 675.0
Subtracting 65 from 65 leaves us with 0.
Fetch the next digit (3) from the dividend, attach it to 0 and continue: 3 / 13

Going ahead to step 5:
3 divided by 13 is 0 with a remainder of 3.
The number 0 becomes the next digit in our result. 
Result so far: 6750.0
The remainder is 3 after subtracting 0 from 3.
Fetch the next digit (5) from the dividend, attach it to 3 and continue: 35 / 13

Going ahead to step 6:
13 goes into 35 2 times with a remainder of 9.
The number 2 becomes the next digit in our result. 
Result so far: 67502.0
Subtracting 26 from 35 leaves us with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Advancing to step 7:
13 goes into 90 6 times with a remainder of 12.
Use 6 as the next digit of our solution. 
Result so far: 67502.6
The remainder is 12 after subtracting 78 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 8:
The number 13 fits into 120 9 times, leaving a remainder of 3.
The number 9 becomes the next digit in our result. 
Result so far: 67502.69
Subtracting 117 from 120 leaves us with 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 9:
30 divided by 13 is 2 with a remainder of 4.
Put 2 as the next digit of the answer. 
Result so far: 67502.692
If we subtract 26 from 30, we get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 10:
If we divide 40 by 13, we get 3 and a remainder of 1.
Put 3 as the next digit of the answer. 
Result so far: 67502.6923
If we subtract 39 from 40, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Step 11:
When dividing 10 by 13, we get 0 with a remainder of 10.
The next digit of our result is 0. 
Result so far: 67502.6923
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.

Going ahead to step 12:
100 divided by 13 is 7 with a remainder of 9.
Record the quotient 7 as the next digit in the result. 
Result so far: 67502.692307
Subtract 91 from 100 to get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

On to step 13:
13 goes into 90 6 times with a remainder of 12.
Use 6 as the next digit of our solution. 
Result so far: 67502.6923076
Subtracting 78 from 90 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Going ahead to step 14:
The number 13 fits into 120 9 times, leaving a remainder of 3.
Record the quotient 9 as the next digit in the result. 
Result so far: 67502.69230769
Subtracting 117 from 120 leaves us with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

The final outcome is 67502.69230769, with a leftover of 3e-09.