664530 ÷ 90 
The aim is to understand the frequency of 90 in 664530.

On to step 1:
6 divided by 90 is 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 / 90

Advancing to step 2:
If we divide 66 by 90, we get 0 and a remainder of 66.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 66 after subtracting 0 from 66.
Grab the next digit (4) from the dividend, add it to 66, then carry on: 664 / 90

Going ahead to step 3:
90 can be fit into 664 7 times, resulting in a remainder of 34.
Use 7 as the next digit of our solution. 
Result so far: 7.0
Deduct 630 from 664 and we're left with 34.
Grab the next digit (5) from the dividend, add it to 34, then carry on: 345 / 90

On to step 4:
90 goes into 345 3 times with a remainder of 75.
Put 3 as the next digit of the answer. 
Result so far: 73.0
Subtracting 270 from 345 leaves us with 75.
Take the next digit (3) from the dividend and append it to 75, then repeat: 753 / 90

Advancing to step 5:
If we divide 753 by 90, we get 8 and a remainder of 33.
Use 8 as the next digit of our solution. 
Result so far: 738.0
If we take 720 away from 753, we end up with 33.
Take the next digit (0) from the dividend and append it to 33, then repeat: 330 / 90

Let's proceed to step 6:
If we divide 330 by 90, we get 3 and a remainder of 60.
Record the quotient 3 as the next digit in the result. 
Result so far: 7383.0
Subtract 270 from 330 to 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.

Step 7:
90 can be fit into 600 6 times, resulting in a remainder of 60.
The next digit of our result is 6. 
Result so far: 7383.6
Subtract 540 from 600 to 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.

Advancing to step 8:
90 goes into 600 6 times with a remainder of 60.
Use 6 as the next digit of our solution. 
Result so far: 7383.66
Deduct 540 from 600 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.

After the division, we end up with 7383.66 and a remainder of 0.06.