Algebra 2
posted by Kenneth .
How many subsets of set T have 2 elemnts if set T has 5 elements?

The number of possible subsets with two elements is the number of combinations possible by choosing two elements out of 5
C(5,2) = 5!/(2!(52)!) = 5*4/2 = 10
For more information, see also:
http://en.wikipedia.org/wiki/Combination