JSFiddle - React, Tailwind, and code Playground

HTML

<select id="id1">
    <option></option>
    <option value="3">3</option>
    <option value="4">4</option>
    <option value="6">6</option>
    <option value="7">7</option>
</select>

<select id="id2">
    <option></option>
    <option value="5">5</option>
    <option value="9">9</option>
</select>

<div id="div1" style="display: none">Div1</div>
<div id="div2" style="display: none"> Div2</div>

JavaScript

$(function() {
    $('#id1, #id2').change(function(){
        
        var tip = $("#id2").val();

        
       if (($('#id1').val() == '3' || $('#id1').val() =='4') && (tip == '5')) 
       {
            alert('primeira div é 3 ou 5 e a segunda é 5');
            $('#div1').fadeIn('slow');
             $('#div2').hide();
        }
       else if ($(this).val() == '6' || $(this).val()  == '7') {
           $('#div1').hide()
       }
        else {
           $('#div2').hide();
           $('#div1').hide();
        }
    });
});