645549 ÷ 18 
The aim is to understand the frequency of 18 in 645549.

Let's proceed to step 1:
18 goes into 6 0 times with a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Bring next digit (4) of the dividend behind the 6 and repeat the process: 64 / 18

Let's proceed to step 2:
The number 18 fits into 64 3 times, leaving a remainder of 10.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Subtract 54 from 64 to get 10.
Include the next digit (5) from the dividend after 10, then repeat: 105 / 18

Step 3:
105 divided by 18 is 5 with a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 35.0
Subtracting 90 from 105 leaves us with 15.
Grab the next digit (5) from the dividend, add it to 15, then carry on: 155 / 18

Moving on to step 4:
The number 18 fits into 155 8 times, leaving a remainder of 11.
The number 8 becomes the next digit in our result. 
Result so far: 358.0
Subtracting 144 from 155 leaves us with 11.
Grab the next digit (4) from the dividend, add it to 11, then carry on: 114 / 18

Step 5:
18 can be fit into 114 6 times, resulting in a remainder of 6.
Use 6 as the next digit of our solution. 
Result so far: 3586.0
Deduct 108 from 114 and we're left with 6.
Fetch the next digit (9) from the dividend, attach it to 6 and continue: 69 / 18

On to step 6:
The number 18 fits into 69 3 times, leaving a remainder of 15.
The next digit of our result is 3. 
Result so far: 35863.0
The remainder is 15 after subtracting 54 from 69.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

On to step 7:
The number 18 fits into 150 8 times, leaving a remainder of 6.
Use 8 as the next digit of our solution. 
Result so far: 35863.8
The remainder is 6 after subtracting 144 from 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Moving on to step 8:
When dividing 60 by 18, we get 3 with a remainder of 6.
Use 3 as the next digit of our solution. 
Result so far: 35863.83
Deduct 54 from 60 and we're left 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 9:
60 divided by 18 is 3 with a remainder of 6.
The next digit of our result is 3. 
Result so far: 35863.833
If we take 54 away from 60, we end up 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.

The final result is 35863.833 with a remainder of 0.0006.