<input type="radio" id="id-5" class="o_input" name="paquetes" value="5">
<input type="radio" id="id-20" class="o_input" name="paquetes" value="20">
<input type="radio" id="id-50" class="o_input" name="paquetes" value="50">
<input type="radio" id="id-100" class="o_input" name="paquetes" value="100">

<input type="hidden" name="quantity" id="quantity" value="10">

$('input.paquetes').click(function(){
    $('#quantity').val($(this).val());
});
/******************************************/
$('input[type=radio]').on('change', function() {
    $('#quantity').val($(this).val());
});
/******************************************/
$('input[type=radio]').on('click', function() {
    $('#quantity').val($(this).val());
});

<div class="modal slideInUp fade text-left animated" id="tokens" tabindex="-1" role="dialog" aria-labelledby="title" aria-hidden="true"></div>