99975541 ÷ 661 
The aim is to understand the frequency of 661 in 99975541.

On to step 1:
If we divide 9 by 661, we get 0 and 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.
Fetch the next digit (9) from the dividend, attach it to 9 and continue: 99 / 661

Let's proceed to step 2:
99 divided by 661 is 0 with a remainder of 99.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 99 leaves us with 99.
Include the next digit (9) from the dividend after 99, then repeat: 999 / 661

Going ahead to step 3:
999 divided by 661 is 1 with a remainder of 338.
Use 1 as the next digit of our solution. 
Result so far: 1.0
If we take 661 away from 999, we end up with 338.
Append the next digit (7) from the dividend to 338 and continue with: 3387 / 661

Step 4:
If we divide 3387 by 661, we get 5 and a remainder of 82.
Use 5 as the next digit of our solution. 
Result so far: 15.0
Subtract 3305 from 3387 to get 82.
Take the next digit (5) from the dividend and append it to 82, then repeat: 825 / 661

Advancing to step 5:
661 can be fit into 825 1 times, resulting in a remainder of 164.
Put 1 as the next digit of the answer. 
Result so far: 151.0
Deduct 661 from 825 and we're left with 164.
Grab the next digit (5) from the dividend, add it to 164, then carry on: 1645 / 661

On to step 6:
When dividing 1645 by 661, we get 2 with a remainder of 323.
Put 2 as the next digit of the answer. 
Result so far: 1512.0
Subtract 1322 from 1645 to get 323.
Fetch the next digit (4) from the dividend, attach it to 323 and continue: 3234 / 661

Going ahead to step 7:
3234 divided by 661 is 4 with a remainder of 590.
Use 4 as the next digit of our solution. 
Result so far: 15124.0
The remainder is 590 after subtracting 2644 from 3234.
Grab the next digit (1) from the dividend, add it to 590, then carry on: 5901 / 661

Step 8:
661 can be fit into 5901 8 times, resulting in a remainder of 613.
The next digit of our result is 8. 
Result so far: 151248.0
Subtract 5288 from 5901 to get 613.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6130, and continue the process.

Step 9:
661 can be fit into 6130 9 times, resulting in a remainder of 181.
Use 9 as the next digit of our solution. 
Result so far: 151248.9
If we take 5949 away from 6130, we end up with 181.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1810, and continue the process.

Moving on to step 10:
If we divide 1810 by 661, we get 2 and a remainder of 488.
Record the quotient 2 as the next digit in the result. 
Result so far: 151248.92
Subtracting 1322 from 1810 leaves us with 488.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4880, and continue the process.

Moving on to step 11:
661 goes into 4880 7 times with a remainder of 253.
The number 7 becomes the next digit in our result. 
Result so far: 151248.927
Subtracting 4627 from 4880 leaves us with 253.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2530, and continue the process.

Going ahead to step 12:
661 goes into 2530 3 times with a remainder of 547.
Record the quotient 3 as the next digit in the result. 
Result so far: 151248.9273
Subtract 1983 from 2530 to get 547.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5470, and continue the process.

Advancing to step 13:
661 can be fit into 5470 8 times, resulting in a remainder of 182.
The next digit of our result is 8. 
Result so far: 151248.92738
Subtract 5288 from 5470 to get 182.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1820, and continue the process.

Step 14:
661 can be fit into 1820 2 times, resulting in a remainder of 498.
Use 2 as the next digit of our solution. 
Result so far: 151248.927382
If we take 1322 away from 1820, we end up with 498.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4980, and continue the process.

Let's proceed to step 15:
661 can be fit into 4980 7 times, resulting in a remainder of 353.
The number 7 becomes the next digit in our result. 
Result so far: 151248.9273827
If we subtract 4627 from 4980, we get 353.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3530, and continue the process.

Moving on to step 16:
3530 divided by 661 is 5 with a remainder of 225.
The number 5 becomes the next digit in our result. 
Result so far: 151248.92738275
If we subtract 3305 from 3530, we get 225.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2250, and continue the process.

The final result is 151248.92738275 with a remainder of 2.25e-07.