123 ÷ 6 = 20 R3
Let's divide 123 by 6.

Step 1:
6 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 1 to get 1.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 6

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

Step 3:
6 goes into 3 0 times with a remainder of 3.
Write down 0 as next digit of of the result. 
Result so far: 20
Subtract 0 from 3 to get 3.

The final result is 20 with a remainder of 3.