791570 ÷ 90 
The aim is to understand the frequency of 90 in 791570.

On to step 1:
When dividing 7 by 90, we get 0 with a remainder of 7.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 7 and we're left with 7.
Fetch the next digit (9) from the dividend, attach it to 7 and continue: 79 / 90

Moving on to step 2:
90 goes into 79 0 times with a remainder of 79.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 79 leaves us with 79.
Append the next digit (1) from the dividend to 79 and continue with: 791 / 90

Advancing to step 3:
791 divided by 90 is 8 with a remainder of 71.
Put 8 as the next digit of the answer. 
Result so far: 8.0
If we subtract 720 from 791, we get 71.
Include the next digit (5) from the dividend after 71, then repeat: 715 / 90

Advancing to step 4:
90 goes into 715 7 times with a remainder of 85.
The number 7 becomes the next digit in our result. 
Result so far: 87.0
The remainder is 85 after subtracting 630 from 715.
Take the next digit (7) from the dividend and append it to 85, then repeat: 857 / 90

Going ahead to step 5:
The number 90 fits into 857 9 times, leaving a remainder of 47.
The number 9 becomes the next digit in our result. 
Result so far: 879.0
Deduct 810 from 857 and we're left with 47.
Grab the next digit (0) from the dividend, add it to 47, then carry on: 470 / 90

Going ahead to step 6:
90 can be fit into 470 5 times, resulting in a remainder of 20.
Put 5 as the next digit of the answer. 
Result so far: 8795.0
If we subtract 450 from 470, we get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

On to step 7:
If we divide 200 by 90, we get 2 and a remainder of 20.
Put 2 as the next digit of the answer. 
Result so far: 8795.2
If we subtract 180 from 200, we get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Let's proceed to step 8:
90 goes into 200 2 times with a remainder of 20.
The next digit of our result is 2. 
Result so far: 8795.22
If we take 180 away from 200, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

The final outcome is 8795.22, with a leftover of 0.02.