12201221 ÷ 678 
We want to divide 12201221 by 678.

On to step 1:
The number 678 fits into 1 0 times, leaving a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 1 after subtracting 0 from 1.
Fetch the next digit (2) from the dividend, attach it to 1 and continue: 12 / 678

Going ahead to step 2:
678 goes into 12 0 times with a remainder of 12.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 12 after subtracting 0 from 12.
Fetch the next digit (2) from the dividend, attach it to 12 and continue: 122 / 678

Moving on to step 3:
678 goes into 122 0 times with a remainder of 122.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 122 and we're left with 122.
Grab the next digit (0) from the dividend, add it to 122, then carry on: 1220 / 678

Moving on to step 4:
678 can be fit into 1220 1 times, resulting in a remainder of 542.
The next digit of our result is 1. 
Result so far: 1.0
If we take 678 away from 1220, we end up with 542.
Fetch the next digit (1) from the dividend, attach it to 542 and continue: 5421 / 678

Going ahead to step 5:
678 can be fit into 5421 7 times, resulting in a remainder of 675.
Put 7 as the next digit of the answer. 
Result so far: 17.0
Subtract 4746 from 5421 to get 675.
Fetch the next digit (2) from the dividend, attach it to 675 and continue: 6752 / 678

Advancing to step 6:
If we divide 6752 by 678, we get 9 and a remainder of 650.
Put 9 as the next digit of the answer. 
Result so far: 179.0
If we subtract 6102 from 6752, we get 650.
Append the next digit (2) from the dividend to 650 and continue with: 6502 / 678

Step 7:
When dividing 6502 by 678, we get 9 with a remainder of 400.
Write down 9 as next digit of the result. 
Result so far: 1799.0
If we take 6102 away from 6502, we end up with 400.
Append the next digit (1) from the dividend to 400 and continue with: 4001 / 678

On to step 8:
678 can be fit into 4001 5 times, resulting in a remainder of 611.
Record the quotient 5 as the next digit in the result. 
Result so far: 17995.0
Subtract 3390 from 4001 to get 611.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6110, and continue the process.

Going ahead to step 9:
If we divide 6110 by 678, we get 9 and a remainder of 8.
The next digit of our result is 9. 
Result so far: 17995.9
The remainder is 8 after subtracting 6102 from 6110.
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 10:
The number 678 fits into 80 0 times, leaving a remainder of 80.
Put 0 as the next digit of the answer. 
Result so far: 17995.9
If we subtract 0 from 80, we get 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

Advancing to step 11:
If we divide 800 by 678, we get 1 and a remainder of 122.
Write down 1 as next digit of the result. 
Result so far: 17995.901
Subtract 678 from 800 to get 122.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1220, and continue the process.

Step 12:
1220 divided by 678 is 1 with a remainder of 542.
Use 1 as the next digit of our solution. 
Result so far: 17995.9011
The remainder is 542 after subtracting 678 from 1220.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5420, and continue the process.

The final outcome is 17995.9011, with a leftover of 0.00542.