The number of all three element subsets of the `{a_1,a_2 ,a_3 ,… a_n}` which contain `a_3 ` is

Find the number of all three elements subsets of the set {a_1, a_2, a_3, a_n} which contain a_3dot

Find the number of all three elements subsets of the set {a_1, a_2, a_3, a_n} which contain a_3dot

Find the number of all three elements subsets of the set {a_1, a_2, a_3, ........... a_n} which contain a_3dot

Find the number of all three elements subsets of the set {a_1, a_2, a_3, ........... a_n} which contain a_3dot

The number all three element ofsubsets of the set A = {a_1 ,a_2 , . . . A_8} contains the element a_3 is

If one quarter of all three element subsets of the set A = { a_1 ,a_2,a_3,. . . ,a_n} contains the element a_3 then n=

Let a_1=0 and a_1,a_2,a_3 …. , a_n be real numbers such that |a_i|=|a_(i-1) + 1| for all I then the A.M. Of the number a_1,a_2 ,a_3 …., a_n has the value A where : (a) A lt -1/2 (b) A lt -1 (c) A ge -1/2 (d) A=-2