We're dividing 509309 by 18 
The aim is to understand the frequency of 18 in 509309.

Going ahead to step 1:
5 divided by 18 is 0 with a remainder of 5.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 5 to get 5.
Bring next digit (0) of the dividend behind the 5 and repeat the process: 50 / 18

Advancing to step 2:
If we divide 50 by 18, we get 2 and a remainder of 14.
The number 2 becomes the next digit in our result. 
Result so far: 2.0
The remainder is 14 after subtracting 36 from 50.
Fetch the next digit (9) from the dividend, attach it to 14 and continue: 149 / 18

On to step 3:
The number 18 fits into 149 8 times, leaving a remainder of 5.
The number 8 becomes the next digit in our result. 
Result so far: 28.0
Deduct 144 from 149 and we're left with 5.
Fetch the next digit (3) from the dividend, attach it to 5 and continue: 53 / 18

Going ahead to step 4:
18 goes into 53 2 times with a remainder of 17.
The next digit of our result is 2. 
Result so far: 282.0
If we subtract 36 from 53, we get 17.
Grab the next digit (0) from the dividend, add it to 17, then carry on: 170 / 18

Let's proceed to step 5:
18 can be fit into 170 9 times, resulting in a remainder of 8.
Record the quotient 9 as the next digit in the result. 
Result so far: 2829.0
If we take 162 away from 170, we end up with 8.
Fetch the next digit (9) from the dividend, attach it to 8 and continue: 89 / 18

Going ahead to step 6:
18 can be fit into 89 4 times, resulting in a remainder of 17.
Record the quotient 4 as the next digit in the result. 
Result so far: 28294.0
If we subtract 72 from 89, we get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Let's proceed to step 7:
18 goes into 170 9 times with a remainder of 8.
The number 9 becomes the next digit in our result. 
Result so far: 28294.9
If we take 162 away from 170, we end up 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.

Advancing to step 8:
18 can be fit into 80 4 times, resulting in a remainder of 8.
The number 4 becomes the next digit in our result. 
Result so far: 28294.94
Subtract 72 from 80 to get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 9:
If we divide 80 by 18, we get 4 and a remainder of 8.
The next digit of our result is 4. 
Result so far: 28294.944
If we subtract 72 from 80, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

The final outcome is 28294.944, with a leftover of 0.0008.