We're dividing 421346 by 12 
Our goal is to divide 421346 by 12.

On to step 1:
12 goes into 4 0 times with a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 4 after subtracting 0 from 4.
Take the next digit (2) from the dividend and append it to 4, then repeat: 42 / 12

On to step 2:
42 divided by 12 is 3 with a remainder of 6.
The number 3 becomes the next digit in our result. 
Result so far: 3.0
If we subtract 36 from 42, we get 6.
Grab the next digit (1) from the dividend, add it to 6, then carry on: 61 / 12

On to step 3:
12 can be fit into 61 5 times, resulting in a remainder of 1.
Record the quotient 5 as the next digit in the result. 
Result so far: 35.0
Deduct 60 from 61 and we're left with 1.
Include the next digit (3) from the dividend after 1, then repeat: 13 / 12

Going ahead to step 4:
12 goes into 13 1 times with a remainder of 1.
Record the quotient 1 as the next digit in the result. 
Result so far: 351.0
If we take 12 away from 13, we end up with 1.
Append the next digit (4) from the dividend to 1 and continue with: 14 / 12

Going ahead to step 5:
12 goes into 14 1 times with a remainder of 2.
The number 1 becomes the next digit in our result. 
Result so far: 3511.0
Subtract 12 from 14 to get 2.
Include the next digit (6) from the dividend after 2, then repeat: 26 / 12

Let's proceed to step 6:
When dividing 26 by 12, we get 2 with a remainder of 2.
Record the quotient 2 as the next digit in the result. 
Result so far: 35112.0
Deduct 24 from 26 and we're left with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

On to step 7:
When dividing 20 by 12, we get 1 with a remainder of 8.
The number 1 becomes the next digit in our result. 
Result so far: 35112.1
Deduct 12 from 20 and we're left with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

On to step 8:
12 can be fit into 80 6 times, resulting in a remainder of 8.
The number 6 becomes the next digit in our result. 
Result so far: 35112.16
The remainder is 8 after subtracting 72 from 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Advancing to step 9:
The number 12 fits into 80 6 times, leaving a remainder of 8.
The number 6 becomes the next digit in our result. 
Result so far: 35112.166
Subtracting 72 from 80 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

The final outcome is 35112.166, with a leftover of 0.0008.