We're dividing 871887 by 90 
The aim is to understand the frequency of 90 in 871887.

Let's proceed to step 1:
The number 90 fits into 8 0 times, leaving a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 8 leaves us with 8.
Take the next digit (7) from the dividend and append it to 8, then repeat: 87 / 90

Advancing to step 2:
If we divide 87 by 90, we get 0 and a remainder of 87.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 87, we end up with 87.
Append the next digit (1) from the dividend to 87 and continue with: 871 / 90

On to step 3:
90 can be fit into 871 9 times, resulting in a remainder of 61.
Record the quotient 9 as the next digit in the result. 
Result so far: 9.0
The remainder is 61 after subtracting 810 from 871.
Append the next digit (8) from the dividend to 61 and continue with: 618 / 90

Step 4:
90 can be fit into 618 6 times, resulting in a remainder of 78.
Write down 6 as next digit of the result. 
Result so far: 96.0
Subtracting 540 from 618 leaves us with 78.
Bring next digit (8) of the dividend behind the 78 and repeat the process: 788 / 90

Let's proceed to step 5:
The number 90 fits into 788 8 times, leaving a remainder of 68.
The next digit of our result is 8. 
Result so far: 968.0
The remainder is 68 after subtracting 720 from 788.
Include the next digit (7) from the dividend after 68, then repeat: 687 / 90

On to step 6:
The number 90 fits into 687 7 times, leaving a remainder of 57.
The number 7 becomes the next digit in our result. 
Result so far: 9687.0
Deduct 630 from 687 and we're left with 57.
Since there are no more digits in the dividend, we add a zero to the remainder making it 570, and continue the process.

Advancing to step 7:
The number 90 fits into 570 6 times, leaving a remainder of 30.
Write down 6 as next digit of the result. 
Result so far: 9687.6
Subtracting 540 from 570 leaves us with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Step 8:
300 divided by 90 is 3 with a remainder of 30.
The next digit of our result is 3. 
Result so far: 9687.63
If we take 270 away from 300, we end up with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Step 9:
90 goes into 300 3 times with a remainder of 30.
Record the quotient 3 as the next digit in the result. 
Result so far: 9687.633
Subtract 270 from 300 to get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

After the division, we end up with 9687.633 and a remainder of 0.003.