If $^nC_{12} = ^nC_6$,then $^nC_2 = $

How many words,with or without meaning,can be formed using all letters of the word $EQUATION$,using each letter exactly once?

The solution set of $^{10}C_{x-1} > 2 \cdot ^{10}C_x$ is

There are $10$ points in a row. In how many ways can $4$ points be selected such that no two of them are consecutive?

There are $m$ men and two women participating in a chess tournament. Each participant plays two games with every other participant. If the number of games played by the men between themselves exceeds the number of games played between the men and the women by $84,$ then the value of $m$ is

The number of four-letter words that can be formed using the letters of the word $BARRACK$ is