738 : 6

1. Divide 7 by 6, which is 1 with a remainder of 1.
2. Bring down the 3 to make 13.
3. Divide 13 by 6, which is 2 with a remainder of 1.
4. Bring down the 8 to make 18.
5. Divide 18 by 6, which is 3.
Result: 123