9903 ÷ 6 = 1650 R3
Alright, let's work through the division of 9903 by 6 step by step.

Step 1:
6 goes into 9 1 times with a remainder of 3.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 6 from 9 to get 3.
Bring next digit (9) of the dividend behind the 3 and repeat the process: 39 / 6

Step 2:
6 goes into 39 6 times with a remainder of 3.
Write down 6 as next digit of of the result. 
Result so far: 16
Subtract 36 from 39 to get 3.
Bring next digit (0) of the dividend behind the 3 and repeat the process: 30 / 6

Step 3:
6 goes into 30 5 times with a remainder of 0.
Write down 5 as next digit of of the result. 
Result so far: 165
Subtract 30 from 30 to get 0.
Bring next digit (3) of the dividend behind the 0 and repeat the process: 3 / 6

Step 4:
6 goes into 3 0 times with a remainder of 3.
Write down 0 as next digit of of the result. 
Result so far: 1650
Subtract 0 from 3 to get 3.

The final result is 1650 with a remainder of 3.