12840 ÷ 30 
We want to divide 12840 by 30.

Moving on to step 1:
When dividing 1 by 30, we get 0 with a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 1, we get 1.
Take the next digit (2) from the dividend and append it to 1, then repeat: 12 / 30

Step 2:
If we divide 12 by 30, we get 0 and a remainder of 12.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 12 leaves us with 12.
Append the next digit (8) from the dividend to 12 and continue with: 128 / 30

Moving on to step 3:
30 goes into 128 4 times with a remainder of 8.
The next digit of our result is 4. 
Result so far: 4.0
If we take 120 away from 128, we end up with 8.
Include the next digit (4) from the dividend after 8, then repeat: 84 / 30

On to step 4:
30 goes into 84 2 times with a remainder of 24.
Use 2 as the next digit of our solution. 
Result so far: 42.0
The remainder is 24 after subtracting 60 from 84.
Grab the next digit (0) from the dividend, add it to 24, then carry on: 240 / 30

Going ahead to step 5:
When dividing 240 by 30, we get 8 with a remainder of 0.
Use 8 as the next digit of our solution. 
Result so far: 428.0
The remainder is 0 after subtracting 240 from 240.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Step 6:
When dividing 0 by 30, we get 0 with a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 428.0
If we subtract 0 from 0, we get 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 7:
The number 30 fits into 0 0 times, leaving a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 428.0
Subtract 0 from 0 to get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Our division results in 428.0 with a remaining 0.0.