We look at the division of 857209 by 18 
The aim is to understand the frequency of 18 in 857209.

On to step 1:
If we divide 8 by 18, we get 0 and a remainder of 8.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 8, we end up with 8.
Take the next digit (5) from the dividend and append it to 8, then repeat: 85 / 18

Step 2:
18 goes into 85 4 times with a remainder of 13.
The next digit of our result is 4. 
Result so far: 4.0
Subtract 72 from 85 to get 13.
Bring next digit (7) of the dividend behind the 13 and repeat the process: 137 / 18

Advancing to step 3:
When dividing 137 by 18, we get 7 with a remainder of 11.
Write down 7 as next digit of the result. 
Result so far: 47.0
If we subtract 126 from 137, we get 11.
Include the next digit (2) from the dividend after 11, then repeat: 112 / 18

Moving on to step 4:
18 goes into 112 6 times with a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 476.0
The remainder is 4 after subtracting 108 from 112.
Include the next digit (0) from the dividend after 4, then repeat: 40 / 18

Moving on to step 5:
18 can be fit into 40 2 times, resulting in a remainder of 4.
Record the quotient 2 as the next digit in the result. 
Result so far: 4762.0
If we take 36 away from 40, we end up with 4.
Include the next digit (9) from the dividend after 4, then repeat: 49 / 18

Moving on to step 6:
The number 18 fits into 49 2 times, leaving a remainder of 13.
Put 2 as the next digit of the answer. 
Result so far: 47622.0
Subtract 36 from 49 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 7:
When dividing 130 by 18, we get 7 with a remainder of 4.
The next digit of our result is 7. 
Result so far: 47622.7
If we subtract 126 from 130, 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 8:
When dividing 40 by 18, we get 2 with a remainder of 4.
The number 2 becomes the next digit in our result. 
Result so far: 47622.72
Deduct 36 from 40 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

On to step 9:
40 divided by 18 is 2 with a remainder of 4.
Record the quotient 2 as the next digit in the result. 
Result so far: 47622.722
Subtracting 36 from 40 leaves us with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Our division results in 47622.722 with a remaining 0.0004.