We look at the division of 458121 by 18 
We want to divide 458121 by 18.

On to step 1:
18 can be fit into 4 0 times, resulting in a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 4, we get 4.
Take the next digit (5) from the dividend and append it to 4, then repeat: 45 / 18

On to step 2:
18 can be fit into 45 2 times, resulting in a remainder of 9.
Record the quotient 2 as the next digit in the result. 
Result so far: 2.0
Subtract 36 from 45 to get 9.
Take the next digit (8) from the dividend and append it to 9, then repeat: 98 / 18

Let's proceed to step 3:
18 goes into 98 5 times with a remainder of 8.
Write down 5 as next digit of the result. 
Result so far: 25.0
Subtract 90 from 98 to get 8.
Fetch the next digit (1) from the dividend, attach it to 8 and continue: 81 / 18

Advancing to step 4:
81 divided by 18 is 4 with a remainder of 9.
Put 4 as the next digit of the answer. 
Result so far: 254.0
Deduct 72 from 81 and we're left with 9.
Take the next digit (2) from the dividend and append it to 9, then repeat: 92 / 18

Going ahead to step 5:
The number 18 fits into 92 5 times, leaving a remainder of 2.
Use 5 as the next digit of our solution. 
Result so far: 2545.0
If we take 90 away from 92, we end up with 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 18

Step 6:
21 divided by 18 is 1 with a remainder of 3.
Use 1 as the next digit of our solution. 
Result so far: 25451.0
The remainder is 3 after subtracting 18 from 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Step 7:
If we divide 30 by 18, we get 1 and a remainder of 12.
Record the quotient 1 as the next digit in the result. 
Result so far: 25451.1
Subtracting 18 from 30 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 8:
When dividing 120 by 18, we get 6 with a remainder of 12.
The number 6 becomes the next digit in our result. 
Result so far: 25451.16
Subtracting 108 from 120 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

On to step 9:
If we divide 120 by 18, we get 6 and a remainder of 12.
The number 6 becomes the next digit in our result. 
Result so far: 25451.166
Deduct 108 from 120 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The final result is 25451.166 with a remainder of 0.0012.