10857 ÷ 21 
We want to divide 10857 by 21.

Advancing to step 1:
If we divide 1 by 21, we get 0 and a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtract 0 from 1 to get 1.
Include the next digit (0) from the dividend after 1, then repeat: 10 / 21

Moving on to step 2:
If we divide 10 by 21, we get 0 and a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 10 and we're left with 10.
Include the next digit (8) from the dividend after 10, then repeat: 108 / 21

Step 3:
If we divide 108 by 21, we get 5 and a remainder of 3.
The number 5 becomes the next digit in our result. 
Result so far: 5.0
Subtract 105 from 108 to get 3.
Fetch the next digit (5) from the dividend, attach it to 3 and continue: 35 / 21

Advancing to step 4:
21 can be fit into 35 1 times, resulting in a remainder of 14.
Record the quotient 1 as the next digit in the result. 
Result so far: 51.0
If we take 21 away from 35, we end up with 14.
Fetch the next digit (7) from the dividend, attach it to 14 and continue: 147 / 21

Step 5:
When dividing 147 by 21, we get 7 with a remainder of 0.
Record the quotient 7 as the next digit in the result. 
Result so far: 517.0
Deduct 147 from 147 and we're left 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.

Moving on to step 6:
The number 21 fits into 0 0 times, leaving a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 517.0
Deduct 0 from 0 and we're left 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.

Advancing to step 7:
If we divide 0 by 21, we get 0 and a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 517.0
Deduct 0 from 0 and we're left 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.

After the division, we end up with 517.0 and a remainder of 0.0.