12390 ÷ 20 
We're looking to find how many times 20 goes into 12390.

Going ahead to step 1:
If we divide 1 by 20, we get 0 and a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 1, we get 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 20

Going ahead to step 2:
When dividing 12 by 20, we get 0 with a remainder of 12.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 12 after subtracting 0 from 12.
Fetch the next digit (3) from the dividend, attach it to 12 and continue: 123 / 20

Moving on to step 3:
20 can be fit into 123 6 times, resulting in a remainder of 3.
Write down 6 as next digit of the result. 
Result so far: 6.0
Subtracting 120 from 123 leaves us with 3.
Grab the next digit (9) from the dividend, add it to 3, then carry on: 39 / 20

Let's proceed to step 4:
If we divide 39 by 20, we get 1 and a remainder of 19.
The next digit of our result is 1. 
Result so far: 61.0
The remainder is 19 after subtracting 20 from 39.
Include the next digit (0) from the dividend after 19, then repeat: 190 / 20

On to step 5:
190 divided by 20 is 9 with a remainder of 10.
The number 9 becomes the next digit in our result. 
Result so far: 619.0
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.

Moving on to step 6:
100 divided by 20 is 5 with a remainder of 0.
Record the quotient 5 as the next digit in the result. 
Result so far: 619.5
The remainder is 0 after subtracting 100 from 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Step 7:
When dividing 0 by 20, we get 0 with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 619.5
If we take 0 away from 0, we end up 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:
0 divided by 20 is 0 with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 619.5
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.

The quotient of the division is 619.5, and the remainder is 0.0.