Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?
$\varnothing \subset A$
State which of the following sets are finite or infinite :
$\{ x:x \in N$ and $x$ is odd $\} $
Write the solution set of the equation ${x^2} + x - 2 = 0$ in roster form.
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 $\} $
Make correct statements by filling in the symbols $\subset$ or $ \not\subset $ in the blank spaces:
$\{a, b, c\} \ldots\{b, c, d\}$