/button>
    </div>
    <div class="card-body">
        <p class="card-text">Explain what is wrong with the following proposed definition of the set
membership predicate <br />
$$ {\forall,x,s;;} x \in {x|s} $$ $$ {\forall,x,s;;} x \in s \implies {\forall,y;;} x \in {y|s} $$
</p>
    </div>
</div>

<p><br /></p>

<div class="card">
    <div class="card-header p-2">
        <a href="ex_20/" class="p-2">Exercise 20 (list-representation-exercise) </a>
        <button type="button" class="btn btn-dark float-rig