18125878 ÷ 399 
We want to divide 18125878 by 399.

Let's proceed to step 1:
399 goes into 1 0 times with a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 1, we get 1.
Fetch the next digit (8) from the dividend, attach it to 1 and continue: 18 / 399

Let's proceed to step 2:
The number 399 fits into 18 0 times, leaving a remainder of 18.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 18 to get 18.
Append the next digit (1) from the dividend to 18 and continue with: 181 / 399

Moving on to step 3:
399 can be fit into 181 0 times, resulting in a remainder of 181.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 181 to get 181.
Take the next digit (2) from the dividend and append it to 181, then repeat: 1812 / 399

On to step 4:
1812 divided by 399 is 4 with a remainder of 216.
Use 4 as the next digit of our solution. 
Result so far: 4.0
Deduct 1596 from 1812 and we're left with 216.
Take the next digit (5) from the dividend and append it to 216, then repeat: 2165 / 399

Step 5:
2165 divided by 399 is 5 with a remainder of 170.
Put 5 as the next digit of the answer. 
Result so far: 45.0
If we subtract 1995 from 2165, we get 170.
Include the next digit (8) from the dividend after 170, then repeat: 1708 / 399

Going ahead to step 6:
When dividing 1708 by 399, we get 4 with a remainder of 112.
Record the quotient 4 as the next digit in the result. 
Result so far: 454.0
If we take 1596 away from 1708, we end up with 112.
Fetch the next digit (7) from the dividend, attach it to 112 and continue: 1127 / 399

On to step 7:
1127 divided by 399 is 2 with a remainder of 329.
Write down 2 as next digit of the result. 
Result so far: 4542.0
If we take 798 away from 1127, we end up with 329.
Grab the next digit (8) from the dividend, add it to 329, then carry on: 3298 / 399

On to step 8:
399 goes into 3298 8 times with a remainder of 106.
Write down 8 as next digit of the result. 
Result so far: 45428.0
If we subtract 3192 from 3298, we get 106.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1060, and continue the process.

Step 9:
399 goes into 1060 2 times with a remainder of 262.
Record the quotient 2 as the next digit in the result. 
Result so far: 45428.2
If we subtract 798 from 1060, we get 262.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2620, and continue the process.

On to step 10:
399 can be fit into 2620 6 times, resulting in a remainder of 226.
The next digit of our result is 6. 
Result so far: 45428.26
The remainder is 226 after subtracting 2394 from 2620.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2260, and continue the process.

Going ahead to step 11:
399 goes into 2260 5 times with a remainder of 265.
The next digit of our result is 5. 
Result so far: 45428.265
Deduct 1995 from 2260 and we're left with 265.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2650, and continue the process.

Let's proceed to step 12:
2650 divided by 399 is 6 with a remainder of 256.
The next digit of our result is 6. 
Result so far: 45428.2656
Deduct 2394 from 2650 and we're left with 256.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2560, and continue the process.

Advancing to step 13:
If we divide 2560 by 399, we get 6 and a remainder of 166.
The number 6 becomes the next digit in our result. 
Result so far: 45428.26566
Deduct 2394 from 2560 and we're left with 166.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1660, and continue the process.

The final outcome is 45428.26566, with a leftover of 0.000166.