We look at the division of 309732 by 18 
The aim is to understand the frequency of 18 in 309732.

Advancing to step 1:
The number 18 fits into 3 0 times, leaving a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 3 and we're left with 3.
Fetch the next digit (0) from the dividend, attach it to 3 and continue: 30 / 18

Let's proceed to step 2:
18 goes into 30 1 times with a remainder of 12.
Use 1 as the next digit of our solution. 
Result so far: 1.0
Subtracting 18 from 30 leaves us with 12.
Append the next digit (9) from the dividend to 12 and continue with: 129 / 18

Step 3:
When dividing 129 by 18, we get 7 with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 17.0
Subtracting 126 from 129 leaves us with 3.
Append the next digit (7) from the dividend to 3 and continue with: 37 / 18

On to step 4:
If we divide 37 by 18, we get 2 and a remainder of 1.
Put 2 as the next digit of the answer. 
Result so far: 172.0
If we take 36 away from 37, we end up with 1.
Bring next digit (3) of the dividend behind the 1 and repeat the process: 13 / 18

Let's proceed to step 5:
The number 18 fits into 13 0 times, leaving a remainder of 13.
The next digit of our result is 0. 
Result so far: 1720.0
Deduct 0 from 13 and we're left with 13.
Fetch the next digit (2) from the dividend, attach it to 13 and continue: 132 / 18

Advancing to step 6:
18 can be fit into 132 7 times, resulting in a remainder of 6.
The number 7 becomes the next digit in our result. 
Result so far: 17207.0
Subtract 126 from 132 to get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 7:
If we divide 60 by 18, we get 3 and a remainder of 6.
Use 3 as the next digit of our solution. 
Result so far: 17207.3
Subtracting 54 from 60 leaves us with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 8:
18 goes into 60 3 times with a remainder of 6.
Put 3 as the next digit of the answer. 
Result so far: 17207.33
Subtract 54 from 60 to get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

The quotient of the division is 17207.33, and the remainder is 0.006.