Rolling dices possibility I must solve given task:
Three dice are rolled. What is possibility the sum of it to be $5$?
I guess I have to use combination formula, but I do not know the basic approach. 
Can you please explain. My thoughts:
Sum of $5$ can be only get from numbers: $1$, $2$ and $3$. - $221$ $113$. I guess those are permutations. How must I continue?

If the outcome the experience is a triplet$\{d_1,d_2,d_3\}$ with the scores of each of the three dice, you have $6^3$ possible outcomes, all with the same probability.
$3$ of these are a permutation of $1-1-3$ and $3$ are a permutation of $1-2-2$
$6$ favourable outcomes in an universe of $6^3$ possible outcomes gives you a probability of $6^{-2}$ of reaching a sum of $5$.
