90105 ÷ 99 
The aim is to understand the frequency of 99 in 90105.

Let's proceed to step 1:
The number 99 fits into 9 0 times, leaving a remainder of 9.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 9 and we're left with 9.
Take the next digit (0) from the dividend and append it to 9, then repeat: 90 / 99

Advancing to step 2:
When dividing 90 by 99, we get 0 with a remainder of 90.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 90, we end up with 90.
Fetch the next digit (1) from the dividend, attach it to 90 and continue: 901 / 99

Moving on to step 3:
If we divide 901 by 99, we get 9 and a remainder of 10.
The number 9 becomes the next digit in our result. 
Result so far: 9.0
If we subtract 891 from 901, we get 10.
Bring next digit (0) of the dividend behind the 10 and repeat the process: 100 / 99

Advancing to step 4:
99 can be fit into 100 1 times, resulting in a remainder of 1.
The next digit of our result is 1. 
Result so far: 91.0
Subtract 99 from 100 to get 1.
Append the next digit (5) from the dividend to 1 and continue with: 15 / 99

On to step 5:
99 goes into 15 0 times with a remainder of 15.
Use 0 as the next digit of our solution. 
Result so far: 910.0
Subtract 0 from 15 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Step 6:
The number 99 fits into 150 1 times, leaving a remainder of 51.
Write down 1 as next digit of the result. 
Result so far: 910.1
If we subtract 99 from 150, we get 51.
Since there are no more digits in the dividend, we add a zero to the remainder making it 510, and continue the process.

Let's proceed to step 7:
99 can be fit into 510 5 times, resulting in a remainder of 15.
The next digit of our result is 5. 
Result so far: 910.15
Deduct 495 from 510 and we're left with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Let's proceed to step 8:
If we divide 150 by 99, we get 1 and a remainder of 51.
The next digit of our result is 1. 
Result so far: 910.151
Deduct 99 from 150 and we're left with 51.
Since there are no more digits in the dividend, we add a zero to the remainder making it 510, and continue the process.

Step 9:
If we divide 510 by 99, we get 5 and a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 910.1515
The remainder is 15 after subtracting 495 from 510.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Let's proceed to step 10:
150 divided by 99 is 1 with a remainder of 51.
Use 1 as the next digit of our solution. 
Result so far: 910.15151
If we subtract 99 from 150, we get 51.
Since there are no more digits in the dividend, we add a zero to the remainder making it 510, and continue the process.

Moving on to step 11:
510 divided by 99 is 5 with a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 910.151515
Deduct 495 from 510 and we're left with 15.
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 12:
If we divide 150 by 99, we get 1 and a remainder of 51.
Use 1 as the next digit of our solution. 
Result so far: 910.1515151
Subtract 99 from 150 to get 51.
Since there are no more digits in the dividend, we add a zero to the remainder making it 510, and continue the process.

Step 13:
If we divide 510 by 99, we get 5 and a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 910.15151515
Subtracting 495 from 510 leaves us with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

The final outcome is 910.15151515, with a leftover of 1.5e-08.