66508311 ÷ 90 
The aim is to understand the frequency of 90 in 66508311.

Moving on to step 1:
6 divided by 90 is 0 with a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Append the next digit (6) from the dividend to 6 and continue with: 66 / 90

Let's proceed to step 2:
66 divided by 90 is 0 with a remainder of 66.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 66, we end up with 66.
Take the next digit (5) from the dividend and append it to 66, then repeat: 665 / 90

Step 3:
The number 90 fits into 665 7 times, leaving a remainder of 35.
Record the quotient 7 as the next digit in the result. 
Result so far: 7.0
If we subtract 630 from 665, we get 35.
Fetch the next digit (0) from the dividend, attach it to 35 and continue: 350 / 90

Let's proceed to step 4:
90 can be fit into 350 3 times, resulting in a remainder of 80.
The next digit of our result is 3. 
Result so far: 73.0
Subtracting 270 from 350 leaves us with 80.
Fetch the next digit (8) from the dividend, attach it to 80 and continue: 808 / 90

Let's proceed to step 5:
When dividing 808 by 90, we get 8 with a remainder of 88.
Use 8 as the next digit of our solution. 
Result so far: 738.0
Subtracting 720 from 808 leaves us with 88.
Grab the next digit (3) from the dividend, add it to 88, then carry on: 883 / 90

On to step 6:
When dividing 883 by 90, we get 9 with a remainder of 73.
Write down 9 as next digit of the result. 
Result so far: 7389.0
Subtracting 810 from 883 leaves us with 73.
Append the next digit (1) from the dividend to 73 and continue with: 731 / 90

Advancing to step 7:
731 divided by 90 is 8 with a remainder of 11.
Put 8 as the next digit of the answer. 
Result so far: 73898.0
If we take 720 away from 731, we end up with 11.
Append the next digit (1) from the dividend to 11 and continue with: 111 / 90

Let's proceed to step 8:
90 can be fit into 111 1 times, resulting in a remainder of 21.
Use 1 as the next digit of our solution. 
Result so far: 738981.0
Deduct 90 from 111 and we're left with 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Advancing to step 9:
The number 90 fits into 210 2 times, leaving a remainder of 30.
The number 2 becomes the next digit in our result. 
Result so far: 738981.2
The remainder is 30 after subtracting 180 from 210.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Let's proceed to step 10:
The number 90 fits into 300 3 times, leaving a remainder of 30.
The next digit of our result is 3. 
Result so far: 738981.23
The remainder is 30 after subtracting 270 from 300.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Step 11:
The number 90 fits into 300 3 times, leaving a remainder of 30.
Use 3 as the next digit of our solution. 
Result so far: 738981.233
The remainder is 30 after subtracting 270 from 300.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

The final outcome is 738981.233, with a leftover of 0.003.