PHP variable to JavaScript variable to HTML span

I'm trying to get a random question in 1 file (a PHP file), and getting that question in another file (a HTML file) that doesn't support PHP. Do you have any idea why/what isn't working?

This is what I already tried:

<?php
    $q = "How much is 5 plus 4?";
?>

<script>
    var qu = <?php echo $q; ?>;
    document.getElementById("quest").innerHTML = this.qu;
</script>

<span id="quest"></span>

Thank you.