40 ÷ 8 = 5 R0
Let's divide 40 by 8.

Step 1:
8 goes into 4 0 times with a remainder of 4.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 4 to get 4.
Bring next digit (0) of the dividend behind the 4 and repeat the process: 40 / 8

Step 2:
8 goes into 40 5 times with a remainder of 0.
Write down 5 as next digit of of the result. 
Result so far: 5
Subtract 40 from 40 to get 0.

The final result is 5 with a remainder of 0.