39966 ÷ 8 = 4995 R6
Let's divide 39966 by 8.

Step 1:
8 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 (9) of the dividend behind the 3 and repeat the process: 39 / 8

Step 2:
8 goes into 39 4 times with a remainder of 7.
Write down 4 as next digit of of the result. 
Result so far: 4
Subtract 32 from 39 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: 49
Subtract 72 from 79 to get 7.
Bring next digit (6) of the dividend behind the 7 and repeat the process: 76 / 8

Step 4:
8 goes into 76 9 times with a remainder of 4.
Write down 9 as next digit of of the result. 
Result so far: 499
Subtract 72 from 76 to get 4.
Bring next digit (6) of the dividend behind the 4 and repeat the process: 46 / 8

Step 5:
8 goes into 46 5 times with a remainder of 6.
Write down 5 as next digit of of the result. 
Result so far: 4995
Subtract 40 from 46 to get 6.

The final result is 4995 with a remainder of 6.