We look at the division of 235678 by 90 
The aim is to understand the frequency of 90 in 235678.

Step 1:
When dividing 2 by 90, we get 0 with a remainder of 2.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 2, we get 2.
Append the next digit (3) from the dividend to 2 and continue with: 23 / 90

Moving on to step 2:
23 divided by 90 is 0 with a remainder of 23.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 23 leaves us with 23.
Append the next digit (5) from the dividend to 23 and continue with: 235 / 90

Step 3:
235 divided by 90 is 2 with a remainder of 55.
Use 2 as the next digit of our solution. 
Result so far: 2.0
Subtract 180 from 235 to get 55.
Bring next digit (6) of the dividend behind the 55 and repeat the process: 556 / 90

Let's proceed to step 4:
If we divide 556 by 90, we get 6 and a remainder of 16.
Put 6 as the next digit of the answer. 
Result so far: 26.0
If we take 540 away from 556, we end up with 16.
Include the next digit (7) from the dividend after 16, then repeat: 167 / 90

Let's proceed to step 5:
When dividing 167 by 90, we get 1 with a remainder of 77.
Record the quotient 1 as the next digit in the result. 
Result so far: 261.0
Deduct 90 from 167 and we're left with 77.
Include the next digit (8) from the dividend after 77, then repeat: 778 / 90

Moving on to step 6:
90 goes into 778 8 times with a remainder of 58.
Use 8 as the next digit of our solution. 
Result so far: 2618.0
Subtract 720 from 778 to get 58.
Since there are no more digits in the dividend, we add a zero to the remainder making it 580, and continue the process.

Let's proceed to step 7:
90 goes into 580 6 times with a remainder of 40.
The number 6 becomes the next digit in our result. 
Result so far: 2618.6
If we take 540 away from 580, we end up with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Advancing to step 8:
90 can be fit into 400 4 times, resulting in a remainder of 40.
Record the quotient 4 as the next digit in the result. 
Result so far: 2618.64
If we subtract 360 from 400, we get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Advancing to step 9:
The number 90 fits into 400 4 times, leaving a remainder of 40.
Record the quotient 4 as the next digit in the result. 
Result so far: 2618.644
The remainder is 40 after subtracting 360 from 400.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Our division results in 2618.644 with a remaining 0.004.