Let's divide 12123515 by 899
We're looking to find how many times 899 goes into 12123515.

Going ahead to step 1:
If we divide 1 by 899, we get 0 and a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Take the next digit (2) from the dividend and append it to 1, then repeat: 12 / 899

Step 2:
12 divided by 899 is 0 with a remainder of 12.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 12, we end up with 12.
Append the next digit (1) from the dividend to 12 and continue with: 121 / 899

Step 3:
If we divide 121 by 899, we get 0 and a remainder of 121.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 121 after subtracting 0 from 121.
Fetch the next digit (2) from the dividend, attach it to 121 and continue: 1212 / 899

Let's proceed to step 4:
1212 divided by 899 is 1 with a remainder of 313.
The next digit of our result is 1. 
Result so far: 1.0
If we subtract 899 from 1212, we get 313.
Append the next digit (3) from the dividend to 313 and continue with: 3133 / 899

Step 5:
The number 899 fits into 3133 3 times, leaving a remainder of 436.
Use 3 as the next digit of our solution. 
Result so far: 13.0
If we subtract 2697 from 3133, we get 436.
Fetch the next digit (5) from the dividend, attach it to 436 and continue: 4365 / 899

Let's proceed to step 6:
If we divide 4365 by 899, we get 4 and a remainder of 769.
Record the quotient 4 as the next digit in the result. 
Result so far: 134.0
The remainder is 769 after subtracting 3596 from 4365.
Fetch the next digit (1) from the dividend, attach it to 769 and continue: 7691 / 899

On to step 7:
899 goes into 7691 8 times with a remainder of 499.
Write down 8 as next digit of the result. 
Result so far: 1348.0
Deduct 7192 from 7691 and we're left with 499.
Include the next digit (5) from the dividend after 499, then repeat: 4995 / 899

On to step 8:
4995 divided by 899 is 5 with a remainder of 500.
Write down 5 as next digit of the result. 
Result so far: 13485.0
The remainder is 500 after subtracting 4495 from 4995.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5000, and continue the process.

Going ahead to step 9:
The number 899 fits into 5000 5 times, leaving a remainder of 505.
The number 5 becomes the next digit in our result. 
Result so far: 13485.5
If we take 4495 away from 5000, we end up with 505.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5050, and continue the process.

Advancing to step 10:
899 can be fit into 5050 5 times, resulting in a remainder of 555.
Put 5 as the next digit of the answer. 
Result so far: 13485.55
Deduct 4495 from 5050 and we're left with 555.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5550, and continue the process.

The final result is 13485.55 with a remainder of 0.555.