78999549 ÷ 639 
Our goal is to divide 78999549 by 639.

Advancing to step 1:
7 divided by 639 is 0 with a remainder of 7.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 7, we end up with 7.
Include the next digit (8) from the dividend after 7, then repeat: 78 / 639

Advancing to step 2:
If we divide 78 by 639, we get 0 and a remainder of 78.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 78 leaves us with 78.
Fetch the next digit (9) from the dividend, attach it to 78 and continue: 789 / 639

Step 3:
639 can be fit into 789 1 times, resulting in a remainder of 150.
The next digit of our result is 1. 
Result so far: 1.0
The remainder is 150 after subtracting 639 from 789.
Grab the next digit (9) from the dividend, add it to 150, then carry on: 1509 / 639

On to step 4:
The number 639 fits into 1509 2 times, leaving a remainder of 231.
The next digit of our result is 2. 
Result so far: 12.0
If we subtract 1278 from 1509, we get 231.
Fetch the next digit (9) from the dividend, attach it to 231 and continue: 2319 / 639

Moving on to step 5:
639 goes into 2319 3 times with a remainder of 402.
The number 3 becomes the next digit in our result. 
Result so far: 123.0
If we subtract 1917 from 2319, we get 402.
Include the next digit (5) from the dividend after 402, then repeat: 4025 / 639

Step 6:
639 goes into 4025 6 times with a remainder of 191.
The number 6 becomes the next digit in our result. 
Result so far: 1236.0
Subtract 3834 from 4025 to get 191.
Append the next digit (4) from the dividend to 191 and continue with: 1914 / 639

Going ahead to step 7:
The number 639 fits into 1914 2 times, leaving a remainder of 636.
Record the quotient 2 as the next digit in the result. 
Result so far: 12362.0
Deduct 1278 from 1914 and we're left with 636.
Take the next digit (9) from the dividend and append it to 636, then repeat: 6369 / 639

Moving on to step 8:
The number 639 fits into 6369 9 times, leaving a remainder of 618.
The next digit of our result is 9. 
Result so far: 123629.0
If we take 5751 away from 6369, we end up with 618.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6180, and continue the process.

On to step 9:
The number 639 fits into 6180 9 times, leaving a remainder of 429.
The next digit of our result is 9. 
Result so far: 123629.9
Subtract 5751 from 6180 to get 429.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4290, and continue the process.

Going ahead to step 10:
4290 divided by 639 is 6 with a remainder of 456.
Record the quotient 6 as the next digit in the result. 
Result so far: 123629.96
Subtracting 3834 from 4290 leaves us with 456.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4560, and continue the process.

On to step 11:
639 goes into 4560 7 times with a remainder of 87.
Put 7 as the next digit of the answer. 
Result so far: 123629.967
If we take 4473 away from 4560, we end up with 87.
Since there are no more digits in the dividend, we add a zero to the remainder making it 870, and continue the process.

Going ahead to step 12:
870 divided by 639 is 1 with a remainder of 231.
The next digit of our result is 1. 
Result so far: 123629.9671
Subtracting 639 from 870 leaves us with 231.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2310, and continue the process.

On to step 13:
639 goes into 2310 3 times with a remainder of 393.
Put 3 as the next digit of the answer. 
Result so far: 123629.96713
If we subtract 1917 from 2310, we get 393.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3930, and continue the process.

Advancing to step 14:
639 goes into 3930 6 times with a remainder of 96.
The next digit of our result is 6. 
Result so far: 123629.967136
Subtracting 3834 from 3930 leaves us with 96.
Since there are no more digits in the dividend, we add a zero to the remainder making it 960, and continue the process.

Going ahead to step 15:
960 divided by 639 is 1 with a remainder of 321.
Write down 1 as next digit of the result. 
Result so far: 123629.9671361
If we take 639 away from 960, we end up with 321.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3210, and continue the process.

Moving on to step 16:
639 can be fit into 3210 5 times, resulting in a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 123629.96713615
Deduct 3195 from 3210 and we're left with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

The final result is 123629.96713615 with a remainder of 1.5e-08.