How to count the subsets of any set

Depends on how many numbers are in the set. Ex. {1,3,5}

the single subset of that set is {1}, {3}, {5}

the double subsets of that set is {1,3}, {1,5}; {3,1}, {3,5}; and the last double subsets are {5,1}, and {5,3}. and then you can count how many subsets you have.