We're dividing 6603999 by 660 
The aim is to understand the frequency of 660 in 6603999.

Advancing to step 1:
660 goes into 6 0 times with a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Fetch the next digit (6) from the dividend, attach it to 6 and continue: 66 / 660

On to step 2:
66 divided by 660 is 0 with a remainder of 66.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 66 and we're left with 66.
Bring next digit (0) of the dividend behind the 66 and repeat the process: 660 / 660

Let's proceed to step 3:
660 divided by 660 is 1 with a remainder of 0.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
If we subtract 660 from 660, we get 0.
Fetch the next digit (3) from the dividend, attach it to 0 and continue: 3 / 660

Going ahead to step 4:
If we divide 3 by 660, we get 0 and a remainder of 3.
The number 0 becomes the next digit in our result. 
Result so far: 10.0
If we take 0 away from 3, we end up with 3.
Include the next digit (9) from the dividend after 3, then repeat: 39 / 660

Let's proceed to step 5:
When dividing 39 by 660, we get 0 with a remainder of 39.
Put 0 as the next digit of the answer. 
Result so far: 100.0
If we subtract 0 from 39, we get 39.
Take the next digit (9) from the dividend and append it to 39, then repeat: 399 / 660

Let's proceed to step 6:
660 goes into 399 0 times with a remainder of 399.
Write down 0 as next digit of the result. 
Result so far: 1000.0
If we subtract 0 from 399, we get 399.
Bring next digit (9) of the dividend behind the 399 and repeat the process: 3999 / 660

Let's proceed to step 7:
660 goes into 3999 6 times with a remainder of 39.
The next digit of our result is 6. 
Result so far: 10006.0
If we subtract 3960 from 3999, we get 39.
Since there are no more digits in the dividend, we add a zero to the remainder making it 390, and continue the process.

Step 8:
390 divided by 660 is 0 with a remainder of 390.
The number 0 becomes the next digit in our result. 
Result so far: 10006.0
Subtracting 0 from 390 leaves us with 390.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3900, and continue the process.

Step 9:
When dividing 3900 by 660, we get 5 with a remainder of 600.
Write down 5 as next digit of the result. 
Result so far: 10006.05
Deduct 3300 from 3900 and we're left with 600.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6000, and continue the process.

Advancing to step 10:
660 goes into 6000 9 times with a remainder of 60.
Record the quotient 9 as the next digit in the result. 
Result so far: 10006.059
Subtracting 5940 from 6000 leaves us with 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

On to step 11:
If we divide 600 by 660, we get 0 and a remainder of 600.
The number 0 becomes the next digit in our result. 
Result so far: 10006.059
If we take 0 away from 600, we end up with 600.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6000, and continue the process.

Going ahead to step 12:
The number 660 fits into 6000 9 times, leaving a remainder of 60.
The next digit of our result is 9. 
Result so far: 10006.05909
Deduct 5940 from 6000 and we're left with 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

Moving on to step 13:
660 can be fit into 600 0 times, resulting in a remainder of 600.
Record the quotient 0 as the next digit in the result. 
Result so far: 10006.05909
Subtract 0 from 600 to get 600.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6000, and continue the process.

On to step 14:
660 can be fit into 6000 9 times, resulting in a remainder of 60.
Put 9 as the next digit of the answer. 
Result so far: 10006.0590909
If we subtract 5940 from 6000, we get 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

On to step 15:
If we divide 600 by 660, we get 0 and a remainder of 600.
Put 0 as the next digit of the answer. 
Result so far: 10006.0590909
Deduct 0 from 600 and we're left with 600.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6000, and continue the process.

The final outcome is 10006.0590909, with a leftover of 6e-07.