71991 ÷ 8 = 8998 R7
We're going to perform division on 71991 with 8 as the divisor.

Step 1:
8 goes into 7 0 times with a remainder of 7.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 7 to get 7.
Bring next digit (1) of the dividend behind the 7 and repeat the process: 71 / 8

Step 2:
8 goes into 71 8 times with a remainder of 7.
Write down 8 as next digit of of the result. 
Result so far: 8
Subtract 64 from 71 to get 7.
Bring next digit (9) of the dividend behind the 7 and repeat the process: 79 / 8

Step 3:
8 goes into 79 9 times with a remainder of 7.
Write down 9 as next digit of of the result. 
Result so far: 89
Subtract 72 from 79 to get 7.
Bring next digit (9) of the dividend behind the 7 and repeat the process: 79 / 8

Step 4:
8 goes into 79 9 times with a remainder of 7.
Write down 9 as next digit of of the result. 
Result so far: 899
Subtract 72 from 79 to get 7.
Bring next digit (1) of the dividend behind the 7 and repeat the process: 71 / 8

Step 5:
8 goes into 71 8 times with a remainder of 7.
Write down 8 as next digit of of the result. 
Result so far: 8998
Subtract 64 from 71 to get 7.

The final result is 8998 with a remainder of 7.