What universal set $(s)$ would you propose for each of the following :
The set of right triangles
Write down all the subsets of the following sets
$\{ a,b\} $
Make correct statements by filling in the symbols $\subset$ or $ \not\subset $ in the blank spaces:
$\{ x:x$ is a student of class $\mathrm{XI}$ of your school $\} \ldots \{ x:x$ student of your school $\} $
State which of the following sets are finite or infinite :
$\{ x:x \in N$ and $x$ is prime $\} $
Let $A, B,$ and $C$ be the sets such that $A \cup B=A \cup C$ and $A \cap B=A \cap C$. Show that $B = C$