We look at the division of 73709642 by 90 
The aim is to understand the frequency of 90 in 73709642.

Advancing to step 1:
If we divide 7 by 90, we get 0 and a remainder of 7.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 7 after subtracting 0 from 7.
Fetch the next digit (3) from the dividend, attach it to 7 and continue: 73 / 90

Let's proceed to step 2:
When dividing 73 by 90, we get 0 with a remainder of 73.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 73, we get 73.
Fetch the next digit (7) from the dividend, attach it to 73 and continue: 737 / 90

On to step 3:
If we divide 737 by 90, we get 8 and a remainder of 17.
Use 8 as the next digit of our solution. 
Result so far: 8.0
Subtracting 720 from 737 leaves us with 17.
Bring next digit (0) of the dividend behind the 17 and repeat the process: 170 / 90

Moving on to step 4:
The number 90 fits into 170 1 times, leaving a remainder of 80.
Put 1 as the next digit of the answer. 
Result so far: 81.0
If we take 90 away from 170, we end up with 80.
Bring next digit (9) of the dividend behind the 80 and repeat the process: 809 / 90

Advancing to step 5:
When dividing 809 by 90, we get 8 with a remainder of 89.
The number 8 becomes the next digit in our result. 
Result so far: 818.0
Deduct 720 from 809 and we're left with 89.
Bring next digit (6) of the dividend behind the 89 and repeat the process: 896 / 90

On to step 6:
When dividing 896 by 90, we get 9 with a remainder of 86.
The next digit of our result is 9. 
Result so far: 8189.0
If we subtract 810 from 896, we get 86.
Fetch the next digit (4) from the dividend, attach it to 86 and continue: 864 / 90

Advancing to step 7:
If we divide 864 by 90, we get 9 and a remainder of 54.
Write down 9 as next digit of the result. 
Result so far: 81899.0
Subtracting 810 from 864 leaves us with 54.
Bring next digit (2) of the dividend behind the 54 and repeat the process: 542 / 90

Moving on to step 8:
When dividing 542 by 90, we get 6 with a remainder of 2.
Record the quotient 6 as the next digit in the result. 
Result so far: 818996.0
Subtracting 540 from 542 leaves us with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Going ahead to step 9:
When dividing 20 by 90, we get 0 with a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 818996.0
If we take 0 away from 20, 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.

Moving on to step 10:
90 can be fit into 200 2 times, resulting in a remainder of 20.
Record the quotient 2 as the next digit in the result. 
Result so far: 818996.02
Deduct 180 from 200 and we're left 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.

Advancing to step 11:
90 goes into 200 2 times with a remainder of 20.
The next digit of our result is 2. 
Result so far: 818996.022
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.

After the division, we end up with 818996.022 and a remainder of 0.002.