We're dividing 355103 by 21 
We want to divide 355103 by 21.

Advancing to step 1:
If we divide 3 by 21, we get 0 and a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Fetch the next digit (5) from the dividend, attach it to 3 and continue: 35 / 21

Let's proceed to step 2:
If we divide 35 by 21, we get 1 and a remainder of 14.
Use 1 as the next digit of our solution. 
Result so far: 1.0
If we take 21 away from 35, we end up with 14.
Grab the next digit (5) from the dividend, add it to 14, then carry on: 145 / 21

Let's proceed to step 3:
21 can be fit into 145 6 times, resulting in a remainder of 19.
The next digit of our result is 6. 
Result so far: 16.0
If we subtract 126 from 145, we get 19.
Take the next digit (1) from the dividend and append it to 19, then repeat: 191 / 21

Moving on to step 4:
If we divide 191 by 21, we get 9 and a remainder of 2.
Use 9 as the next digit of our solution. 
Result so far: 169.0
Subtract 189 from 191 to get 2.
Fetch the next digit (0) from the dividend, attach it to 2 and continue: 20 / 21

Step 5:
21 can be fit into 20 0 times, resulting in a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 1690.0
If we subtract 0 from 20, we get 20.
Grab the next digit (3) from the dividend, add it to 20, then carry on: 203 / 21

Step 6:
The number 21 fits into 203 9 times, leaving a remainder of 14.
The number 9 becomes the next digit in our result. 
Result so far: 16909.0
Deduct 189 from 203 and we're left with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Let's proceed to step 7:
21 goes into 140 6 times with a remainder of 14.
The number 6 becomes the next digit in our result. 
Result so far: 16909.6
Deduct 126 from 140 and we're left with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Moving on to step 8:
21 can be fit into 140 6 times, resulting in a remainder of 14.
The number 6 becomes the next digit in our result. 
Result so far: 16909.66
If we subtract 126 from 140, we get 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

The final outcome is 16909.66, with a leftover of 0.014.