603240 ÷ 12 
We're looking to find how many times 12 goes into 603240.

Step 1:
If we divide 6 by 12, we get 0 and a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Include the next digit (0) from the dividend after 6, then repeat: 60 / 12

Step 2:
If we divide 60 by 12, we get 5 and a remainder of 0.
Write down 5 as next digit of the result. 
Result so far: 5.0
Deduct 60 from 60 and we're left with 0.
Include the next digit (3) from the dividend after 0, then repeat: 3 / 12

Advancing to step 3:
If we divide 3 by 12, we get 0 and a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 50.0
Deduct 0 from 3 and we're left with 3.
Include the next digit (2) from the dividend after 3, then repeat: 32 / 12

Moving on to step 4:
32 divided by 12 is 2 with a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 502.0
If we take 24 away from 32, we end up with 8.
Grab the next digit (4) from the dividend, add it to 8, then carry on: 84 / 12

Advancing to step 5:
The number 12 fits into 84 7 times, leaving a remainder of 0.
Use 7 as the next digit of our solution. 
Result so far: 5027.0
Deduct 84 from 84 and we're left with 0.
Take the next digit (0) from the dividend and append it to 0, then repeat: 0 / 12

Going ahead to step 6:
When dividing 0 by 12, we get 0 with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 50270.0
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.

On to step 7:
0 divided by 12 is 0 with a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 50270.0
If we take 0 away from 0, we end up 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 8:
If we divide 0 by 12, we get 0 and a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 50270.0
Subtracting 0 from 0 leaves us 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.

Our division results in 50270.0 with a remaining 0.0.