We look at the division of 66517554 by 543 
The aim is to understand the frequency of 543 in 66517554.

Advancing to step 1:
When dividing 6 by 543, we get 0 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.
Append the next digit (6) from the dividend to 6 and continue with: 66 / 543

Step 2:
If we divide 66 by 543, we get 0 and a remainder of 66.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 66 and we're left with 66.
Grab the next digit (5) from the dividend, add it to 66, then carry on: 665 / 543

Going ahead to step 3:
The number 543 fits into 665 1 times, leaving a remainder of 122.
Write down 1 as next digit of the result. 
Result so far: 1.0
Subtracting 543 from 665 leaves us with 122.
Fetch the next digit (1) from the dividend, attach it to 122 and continue: 1221 / 543

Step 4:
543 goes into 1221 2 times with a remainder of 135.
Record the quotient 2 as the next digit in the result. 
Result so far: 12.0
If we subtract 1086 from 1221, we get 135.
Grab the next digit (7) from the dividend, add it to 135, then carry on: 1357 / 543

Advancing to step 5:
The number 543 fits into 1357 2 times, leaving a remainder of 271.
Record the quotient 2 as the next digit in the result. 
Result so far: 122.0
If we take 1086 away from 1357, we end up with 271.
Fetch the next digit (5) from the dividend, attach it to 271 and continue: 2715 / 543

Advancing to step 6:
The number 543 fits into 2715 5 times, leaving a remainder of 0.
Put 5 as the next digit of the answer. 
Result so far: 1225.0
If we take 2715 away from 2715, we end up with 0.
Take the next digit (5) from the dividend and append it to 0, then repeat: 5 / 543

Going ahead to step 7:
When dividing 5 by 543, we get 0 with a remainder of 5.
Write down 0 as next digit of the result. 
Result so far: 12250.0
Subtracting 0 from 5 leaves us with 5.
Take the next digit (4) from the dividend and append it to 5, then repeat: 54 / 543

Step 8:
543 can be fit into 54 0 times, resulting in a remainder of 54.
The number 0 becomes the next digit in our result. 
Result so far: 122500.0
Subtracting 0 from 54 leaves us with 54.
Since there are no more digits in the dividend, we add a zero to the remainder making it 540, and continue the process.

Let's proceed to step 9:
543 can be fit into 540 0 times, resulting in a remainder of 540.
Record the quotient 0 as the next digit in the result. 
Result so far: 122500.0
Deduct 0 from 540 and we're left with 540.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5400, and continue the process.

On to step 10:
5400 divided by 543 is 9 with a remainder of 513.
The next digit of our result is 9. 
Result so far: 122500.09
If we subtract 4887 from 5400, we get 513.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5130, and continue the process.

Moving on to step 11:
When dividing 5130 by 543, we get 9 with a remainder of 243.
Use 9 as the next digit of our solution. 
Result so far: 122500.099
If we take 4887 away from 5130, we end up with 243.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2430, and continue the process.

Our division results in 122500.099 with a remaining 0.0243.