$\left\{ X: X \in \{\{1,2\},\{1,3\},\{2,3\},\{2,4\}\} \wedge x \not\subseteq \{2,3,4\} \right\} = A$
Well, I did some work on it and I've found that $ A=\{\{1,2\},\{1,3\}\} $.
which means $|A| = 2$
Is that true? also, if possible, I'd like to see how you solve it.
(I know I could write it better, just was lazy)
)