We look at the division of 51858 by 81 
We want to divide 51858 by 81.

Going ahead to step 1:
5 divided by 81 is 0 with a remainder of 5.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 5, we end up with 5.
Fetch the next digit (1) from the dividend, attach it to 5 and continue: 51 / 81

On to step 2:
81 can be fit into 51 0 times, resulting in a remainder of 51.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 51, we get 51.
Include the next digit (8) from the dividend after 51, then repeat: 518 / 81

Step 3:
81 can be fit into 518 6 times, resulting in a remainder of 32.
Put 6 as the next digit of the answer. 
Result so far: 6.0
Subtract 486 from 518 to get 32.
Include the next digit (5) from the dividend after 32, then repeat: 325 / 81

Step 4:
When dividing 325 by 81, we get 4 with a remainder of 1.
Record the quotient 4 as the next digit in the result. 
Result so far: 64.0
The remainder is 1 after subtracting 324 from 325.
Append the next digit (8) from the dividend to 1 and continue with: 18 / 81

Let's proceed to step 5:
The number 81 fits into 18 0 times, leaving a remainder of 18.
Record the quotient 0 as the next digit in the result. 
Result so far: 640.0
If we subtract 0 from 18, we get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

On to step 6:
When dividing 180 by 81, we get 2 with a remainder of 18.
The next digit of our result is 2. 
Result so far: 640.2
If we subtract 162 from 180, we get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 7:
180 divided by 81 is 2 with a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 640.22
Deduct 162 from 180 and we're left with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

The final result is 640.22 with a remainder of 0.018.