Question

WHAT IS THE CARDINALITY OF {a,{a},{a,{a}}}

Answer 1

The cardinality of any finite set is just the number of its elements. The elements of the set $\{a,\{a\},\{a,\{a\}\}\}$ are:

1. $a$
2. $\{a\}$
3. $\{a,\{a\}\}$

So the cardinality is $|\{a,\{a\},\{a,\{a\}\}\}|=3.$