We look at the division of 903908 by 18 
The aim is to understand the frequency of 18 in 903908.

Going ahead to step 1:
18 goes into 9 0 times with a remainder of 9.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 9 after subtracting 0 from 9.
Include the next digit (0) from the dividend after 9, then repeat: 90 / 18

Step 2:
18 goes into 90 5 times with a remainder of 0.
Record the quotient 5 as the next digit in the result. 
Result so far: 5.0
If we subtract 90 from 90, we get 0.
Fetch the next digit (3) from the dividend, attach it to 0 and continue: 3 / 18

Moving on to step 3:
18 can be fit into 3 0 times, resulting in a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 50.0
The remainder is 3 after subtracting 0 from 3.
Take the next digit (9) from the dividend and append it to 3, then repeat: 39 / 18

Going ahead to step 4:
The number 18 fits into 39 2 times, leaving a remainder of 3.
Write down 2 as next digit of the result. 
Result so far: 502.0
Subtracting 36 from 39 leaves us with 3.
Append the next digit (0) from the dividend to 3 and continue with: 30 / 18

Going ahead to step 5:
18 goes into 30 1 times with a remainder of 12.
Use 1 as the next digit of our solution. 
Result so far: 5021.0
Subtract 18 from 30 to get 12.
Bring next digit (8) of the dividend behind the 12 and repeat the process: 128 / 18

Advancing to step 6:
18 can be fit into 128 7 times, resulting in a remainder of 2.
Put 7 as the next digit of the answer. 
Result so far: 50217.0
Subtract 126 from 128 to get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Going ahead to step 7:
18 can be fit into 20 1 times, resulting in a remainder of 2.
Use 1 as the next digit of our solution. 
Result so far: 50217.1
If we take 18 away from 20, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 8:
When dividing 20 by 18, we get 1 with a remainder of 2.
Use 1 as the next digit of our solution. 
Result so far: 50217.11
If we subtract 18 from 20, we get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

The quotient of the division is 50217.11, and the remainder is 0.002.