Let's divide 354090 by 18
The aim is to understand the frequency of 18 in 354090.

Advancing to step 1:
When dividing 3 by 18, we get 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 3, we end up with 3.
Take the next digit (5) from the dividend and append it to 3, then repeat: 35 / 18

Going ahead to step 2:
18 can be fit into 35 1 times, resulting in a remainder of 17.
Use 1 as the next digit of our solution. 
Result so far: 1.0
Subtracting 18 from 35 leaves us with 17.
Bring next digit (4) of the dividend behind the 17 and repeat the process: 174 / 18

Going ahead to step 3:
18 can be fit into 174 9 times, resulting in a remainder of 12.
The number 9 becomes the next digit in our result. 
Result so far: 19.0
If we take 162 away from 174, we end up with 12.
Fetch the next digit (0) from the dividend, attach it to 12 and continue: 120 / 18

Step 4:
120 divided by 18 is 6 with a remainder of 12.
Record the quotient 6 as the next digit in the result. 
Result so far: 196.0
The remainder is 12 after subtracting 108 from 120.
Fetch the next digit (9) from the dividend, attach it to 12 and continue: 129 / 18

Step 5:
The number 18 fits into 129 7 times, leaving a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 1967.0
The remainder is 3 after subtracting 126 from 129.
Grab the next digit (0) from the dividend, add it to 3, then carry on: 30 / 18

Let's proceed to step 6:
The number 18 fits into 30 1 times, leaving a remainder of 12.
Record the quotient 1 as the next digit in the result. 
Result so far: 19671.0
Subtracting 18 from 30 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Advancing to step 7:
18 goes into 120 6 times with a remainder of 12.
The number 6 becomes the next digit in our result. 
Result so far: 19671.6
The remainder is 12 after subtracting 108 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 8:
120 divided by 18 is 6 with a remainder of 12.
The number 6 becomes the next digit in our result. 
Result so far: 19671.66
Subtract 108 from 120 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The final result is 19671.66 with a remainder of 0.012.