We're dividing 63990 by 75 
We're looking to find how many times 75 goes into 63990.

Moving on to step 1:
If we divide 6 by 75, we get 0 and a remainder of 6.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Append the next digit (3) from the dividend to 6 and continue with: 63 / 75

Moving on to step 2:
The number 75 fits into 63 0 times, leaving a remainder of 63.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 63 leaves us with 63.
Fetch the next digit (9) from the dividend, attach it to 63 and continue: 639 / 75

Advancing to step 3:
If we divide 639 by 75, we get 8 and a remainder of 39.
Write down 8 as next digit of the result. 
Result so far: 8.0
The remainder is 39 after subtracting 600 from 639.
Bring next digit (9) of the dividend behind the 39 and repeat the process: 399 / 75

Advancing to step 4:
399 divided by 75 is 5 with a remainder of 24.
Use 5 as the next digit of our solution. 
Result so far: 85.0
If we subtract 375 from 399, we get 24.
Bring next digit (0) of the dividend behind the 24 and repeat the process: 240 / 75

Let's proceed to step 5:
75 goes into 240 3 times with a remainder of 15.
The number 3 becomes the next digit in our result. 
Result so far: 853.0
If we take 225 away from 240, we end up 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.

Moving on to step 6:
If we divide 150 by 75, we get 2 and a remainder of 0.
Put 2 as the next digit of the answer. 
Result so far: 853.2
Subtract 150 from 150 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.

Advancing to step 7:
75 can be fit into 0 0 times, resulting in a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 853.2
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.

On to step 8:
75 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 853.2
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.

The final result is 853.2 with a remainder of 0.0.