Let's divide 309918 by 18
Let's see how many times 18 fits into 309918.

Advancing to step 1:
18 goes into 3 0 times with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Fetch the next digit (0) from the dividend, attach it to 3 and continue: 30 / 18

Moving on to step 2:
18 goes into 30 1 times with a remainder of 12.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
If we take 18 away from 30, we end up with 12.
Append the next digit (9) from the dividend to 12 and continue with: 129 / 18

Let's proceed to step 3:
18 goes into 129 7 times with a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 17.0
Subtract 126 from 129 to get 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 18

Moving on to step 4:
18 goes into 39 2 times with a remainder of 3.
The next digit of our result is 2. 
Result so far: 172.0
If we take 36 away from 39, we end up with 3.
Bring next digit (1) of the dividend behind the 3 and repeat the process: 31 / 18

Step 5:
18 can be fit into 31 1 times, resulting in a remainder of 13.
Record the quotient 1 as the next digit in the result. 
Result so far: 1721.0
If we take 18 away from 31, we end up with 13.
Grab the next digit (8) from the dividend, add it to 13, then carry on: 138 / 18

Let's proceed to step 6:
18 can be fit into 138 7 times, resulting in a remainder of 12.
Record the quotient 7 as the next digit in the result. 
Result so far: 17217.0
Subtracting 126 from 138 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Going ahead to step 7:
If we divide 120 by 18, we get 6 and a remainder of 12.
Put 6 as the next digit of the answer. 
Result so far: 17217.6
Deduct 108 from 120 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

On to step 8:
18 can be fit into 120 6 times, resulting in a remainder of 12.
The next digit of our result is 6. 
Result so far: 17217.66
If we subtract 108 from 120, we get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The final outcome is 17217.66, with a leftover of 0.012.