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I have 3 buttons outside the form tag and when clicking on some of them, I need the value to be selected in select, follow image and code for better understanding:
Buttons (outside the tag form)
<div class="botoes_action">
  <div class="col-lg-4 col-md-4 col-sm-4 col-xs-12">
    <a href="">
      <button class="botao_preto waves-effect waves-light">
        Compre 3 unidades 
        <b>
          receba 1 de brinde
        </b>
      </button>
    </a>
  </div>
  <div class="col-lg-4 col-md-4 col-sm-4 col-xs-12">
    <a href="">
      <button class="botao_vermelho waves-effect waves-light">
        Compre 5 unidades 
        <b>
          receba 2 de brinde
        </b>
      </button>
    </a>
  </div>
  <div class="col-lg-4 col-md-4 col-sm-4 col-xs-12">
    <a href="">
      <button class="botao_verde waves-effect waves-light">
        Compre 10 unidades 
        <b>
          receba 5 de brinde
        </b>
      </button>
    </a>
  </div>
</div>
 <form class="formulario_area" action="#" id="form_envio" method="post">
   <div class="row">
     <div class="input-field col m12 s12 paddingNone">
       <input type="text" class="form-control box_form" required="" id="nome" name="nome" placeholder="Nome Completo">
     </div>
     <div class="input-field col m12 s12 paddingNone">
       <input type="text" class="form-control box_form" required="" id="email" name="email" placeholder="E-mail">
     </div>
     <div class="input-field col m12 s12 paddingNone paddingL">
       <input type="text" class="form-control box_form" required="" id="telefone" name="telefone" placeholder="Telefone">
     </div>
     <div class=" col m6 s12 paddingNone paddingL">
       <select name="estado" class="form-control box_form" required="" id="estado" onchange="mudaCidade($(this).val());">
       </select>
     </div>
     <div class="col m6 s12 paddingNone paddingL">
       <select name="cidade" class="form-control box_form" required="" id="cidade">
         <option value="cidade">Cidade</option>                           
       </select>
     </div>
     <div class="form-group col m12 s12 paddingNone paddingL">
       <select name="pacote" class="form-control box_form" required="" id="pacote">
         <option value="" selected="" disabled="">Escolha uma unidade</option>  
         <option value="3">3 Unidades</option>       
         <option value="5">5 Unidades</option>   
         <option value="10">10 Unidades</option>                       
       </select>
     </div>                                    
   </div>                               
   <div class="col-lg-12 col-md-12 col-sm-12 col-xs-12 send_btn">
     <button class="waves-effect waves-light btn button_send" data-loading-text="Aguarde..." type="submit">
       Enviar
     </button>
   </div>
</form>When clicking one of the three buttons, I need the last field of the form (unit) to be preselected. But I have no idea how to do this; Someone has already had to do something similar and can give some hint?
This way the user cannot select another value after clicking on the 3 buttons.
– JuniorNunes