3609 ÷ 3 = 1203 R0
Let's divide 3609 by 3.

Step 1:
3 goes into 3 1 times with a remainder of 0.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 3 from 3 to get 0.
Bring next digit (6) of the dividend behind the 0 and repeat the process: 6 / 3

Step 2:
3 goes into 6 2 times with a remainder of 0.
Write down 2 as next digit of of the result. 
Result so far: 12
Subtract 6 from 6 to get 0.
Bring next digit (0) of the dividend behind the 0 and repeat the process: 0 / 3

Step 3:
3 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of of the result. 
Result so far: 120
Subtract 0 from 0 to get 0.
Bring next digit (9) of the dividend behind the 0 and repeat the process: 9 / 3

Step 4:
3 goes into 9 3 times with a remainder of 0.
Write down 3 as next digit of of the result. 
Result so far: 1203
Subtract 9 from 9 to get 0.

The final result is 1203 with a remainder of 0.