We're dividing 623990 by 20 
The aim is to understand the frequency of 20 in 623990.

On to step 1:
If we divide 6 by 20, we get 0 and a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Grab the next digit (2) from the dividend, add it to 6, then carry on: 62 / 20

Going ahead to step 2:
62 divided by 20 is 3 with a remainder of 2.
Put 3 as the next digit of the answer. 
Result so far: 3.0
If we subtract 60 from 62, we get 2.
Append the next digit (3) from the dividend to 2 and continue with: 23 / 20

Advancing to step 3:
20 goes into 23 1 times with a remainder of 3.
Put 1 as the next digit of the answer. 
Result so far: 31.0
Deduct 20 from 23 and we're left with 3.
Include the next digit (9) from the dividend after 3, then repeat: 39 / 20

Step 4:
If we divide 39 by 20, we get 1 and a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 311.0
If we take 20 away from 39, we end up with 19.
Take the next digit (9) from the dividend and append it to 19, then repeat: 199 / 20

Step 5:
The number 20 fits into 199 9 times, leaving a remainder of 19.
Record the quotient 9 as the next digit in the result. 
Result so far: 3119.0
Subtracting 180 from 199 leaves us with 19.
Include the next digit (0) from the dividend after 19, then repeat: 190 / 20

Going ahead to step 6:
190 divided by 20 is 9 with a remainder of 10.
Put 9 as the next digit of the answer. 
Result so far: 31199.0
Deduct 180 from 190 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.

Step 7:
20 goes into 100 5 times with a remainder of 0.
The next digit of our result is 5. 
Result so far: 31199.5
Subtracting 100 from 100 leaves us with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

On to step 8:
When dividing 0 by 20, we get 0 with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 31199.5
If we subtract 0 from 0, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Advancing to step 9:
The number 20 fits into 0 0 times, leaving a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 31199.5
The remainder is 0 after subtracting 0 from 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The quotient of the division is 31199.5, and the remainder is 0.0.