What is the probability of getting a sum 13 from three throws of a dice?

Answer 1

i THINK 21/216 (or 7/72)BECAUSE
1,6,6 group can happen in three ways
2,5,6 group can happen in six ways
3,4,6 group can happen in six ways
3,5,5 group can happen in three ways
and 4,4,5 group can happen in three ways
giving the total number of combinations for sum 13 equal to 21 out of total of 216