JSFiddle - React, Tailwind, and code Playground

HTML

<div id="marqueurs">
    <div class="marqueur">
        <p>Points à récupérer : <span class="pointsXP">10</span></p>
        <button class="recupererXP">Récupérer</button>
    </div>
    <br/>
    <div class="marqueur">
        <p>Points à récupérer : <span class="pointsXP">5</span></p>
        <button class="recupererXP">Récupérer</button>
    </div>
</div>
<p>Points cumulés : <span id="totalXP">2</span></p>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

JavaScript

$('#marqueurs').on('click', '.marqueur button', function() {
    var currentXP = $("#totalXP").text();
    var xpToWin = $(this).parents('.marqueur').find('.pointsXP').text();
    $(".recupererXP").click(function() {    
        var newValue = parseInt(xpToWin) + parseInt(currentXP);                                  
        $('#totalXP').text(newValue);
    });
 })