1 votes 1 votes Can someone explain me the solution of this problem? Set Theory & Algebra counting + – MrPeppermint asked Nov 10, 2017 MrPeppermint 271 views answer comment Share Follow See 1 comment See all 1 1 comment reply saxena0612 commented Nov 11, 2017 reply Follow Share For every element you have 2 choices either to select it or not ! I think here you start with $\phi$ and then for every element draw a tree either to choose it or not. ---------------------------------------------------------------------------------------------------------------------------------------------------------- you will have 2x leaves Something like this: And Called as Power Set where you have every possible set of a given element set. 3 votes 3 votes Please log in or register to add a comment.