We look at the division of 978589 by 90 
The aim is to understand the frequency of 90 in 978589.

Advancing to step 1:
When dividing 9 by 90, we get 0 with a remainder of 9.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 9 and we're left with 9.
Include the next digit (7) from the dividend after 9, then repeat: 97 / 90

Advancing to step 2:
97 divided by 90 is 1 with a remainder of 7.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Subtracting 90 from 97 leaves us with 7.
Include the next digit (8) from the dividend after 7, then repeat: 78 / 90

On to step 3:
When dividing 78 by 90, we get 0 with a remainder of 78.
Record the quotient 0 as the next digit in the result. 
Result so far: 10.0
Subtracting 0 from 78 leaves us with 78.
Fetch the next digit (5) from the dividend, attach it to 78 and continue: 785 / 90

Advancing to step 4:
When dividing 785 by 90, we get 8 with a remainder of 65.
Use 8 as the next digit of our solution. 
Result so far: 108.0
The remainder is 65 after subtracting 720 from 785.
Fetch the next digit (8) from the dividend, attach it to 65 and continue: 658 / 90

Advancing to step 5:
658 divided by 90 is 7 with a remainder of 28.
Write down 7 as next digit of the result. 
Result so far: 1087.0
If we subtract 630 from 658, we get 28.
Take the next digit (9) from the dividend and append it to 28, then repeat: 289 / 90

Step 6:
If we divide 289 by 90, we get 3 and a remainder of 19.
The number 3 becomes the next digit in our result. 
Result so far: 10873.0
If we take 270 away from 289, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 7:
190 divided by 90 is 2 with a remainder of 10.
The next digit of our result is 2. 
Result so far: 10873.2
If we take 180 away from 190, we end up with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Advancing to step 8:
100 divided by 90 is 1 with a remainder of 10.
The number 1 becomes the next digit in our result. 
Result so far: 10873.21
Deduct 90 from 100 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On to step 9:
If we divide 100 by 90, we get 1 and a remainder of 10.
The next digit of our result is 1. 
Result so far: 10873.211
If we take 90 away from 100, we end up with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

After the division, we end up with 10873.211 and a remainder of 0.001.