31991 ÷ 9 = 3554 R5
We're going to perform division on 31991 with 9 as the divisor.

Step 1:
9 goes into 3 0 times with a remainder of 3.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 3 to get 3.
Bring next digit (1) of the dividend behind the 3 and repeat the process: 31 / 9

Step 2:
9 goes into 31 3 times with a remainder of 4.
Write down 3 as next digit of of the result. 
Result so far: 3
Subtract 27 from 31 to get 4.
Bring next digit (9) of the dividend behind the 4 and repeat the process: 49 / 9

Step 3:
9 goes into 49 5 times with a remainder of 4.
Write down 5 as next digit of of the result. 
Result so far: 35
Subtract 45 from 49 to get 4.
Bring next digit (9) of the dividend behind the 4 and repeat the process: 49 / 9

Step 4:
9 goes into 49 5 times with a remainder of 4.
Write down 5 as next digit of of the result. 
Result so far: 355
Subtract 45 from 49 to get 4.
Bring next digit (1) of the dividend behind the 4 and repeat the process: 41 / 9

Step 5:
9 goes into 41 4 times with a remainder of 5.
Write down 4 as next digit of of the result. 
Result so far: 3554
Subtract 36 from 41 to get 5.

The final result is 3554 with a remainder of 5.