We look at the division of 681721 by 18 
The aim is to understand the frequency of 18 in 681721.

Step 1:
When dividing 6 by 18, we get 0 with a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Fetch the next digit (8) from the dividend, attach it to 6 and continue: 68 / 18

Going ahead to step 2:
18 goes into 68 3 times with a remainder of 14.
Write down 3 as next digit of the result. 
Result so far: 3.0
Subtract 54 from 68 to get 14.
Grab the next digit (1) from the dividend, add it to 14, then carry on: 141 / 18

Advancing to step 3:
141 divided by 18 is 7 with a remainder of 15.
Record the quotient 7 as the next digit in the result. 
Result so far: 37.0
Subtract 126 from 141 to get 15.
Fetch the next digit (7) from the dividend, attach it to 15 and continue: 157 / 18

Let's proceed to step 4:
18 can be fit into 157 8 times, resulting in a remainder of 13.
Record the quotient 8 as the next digit in the result. 
Result so far: 378.0
If we subtract 144 from 157, we get 13.
Include the next digit (2) from the dividend after 13, then repeat: 132 / 18

On to step 5:
The number 18 fits into 132 7 times, leaving a remainder of 6.
The next digit of our result is 7. 
Result so far: 3787.0
If we take 126 away from 132, we end up with 6.
Grab the next digit (1) from the dividend, add it to 6, then carry on: 61 / 18

Let's proceed to step 6:
When dividing 61 by 18, we get 3 with a remainder of 7.
The number 3 becomes the next digit in our result. 
Result so far: 37873.0
If we take 54 away from 61, we end up with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

On to step 7:
When dividing 70 by 18, we get 3 with a remainder of 16.
Record the quotient 3 as the next digit in the result. 
Result so far: 37873.3
The remainder is 16 after subtracting 54 from 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Step 8:
18 goes into 160 8 times with a remainder of 16.
The next digit of our result is 8. 
Result so far: 37873.38
If we take 144 away from 160, we end up with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Advancing to step 9:
18 can be fit into 160 8 times, resulting in a remainder of 16.
Write down 8 as next digit of the result. 
Result so far: 37873.388
Subtract 144 from 160 to get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

In conclusion, the division gives 37873.388 with a balance of 0.0016.