From Pairs to Triples

Difficulty: Easy · Topics: Discrete Mathematics, Sets, Subsets

All the two-element subsets of a set A are written below.

\1,4\, \2,1\, \2,4\

\2,\2,3\\, \1,\2,3\\, \4,\2,3\\

How many three-element subsets does the set A have?