Hello chengbinThe possible scores are:

- one 4 and two 1's. The number of ways of choosing which of the three dice shows the 4 is .
- one 3, one 2 and one 1. The three dice can be arranged to show these scores in ways.
- three 2's. There is no choice involved; all the dice must show the same number. This can be done in (or ) ways.

Thus .

LaTeX answer: enclose ^3C_1 in {...}

Grandad