Esto es lo que hice yo.
Código
<section class="row"> <div class="col-md-8 d-md-block d-lg-block d-none"> <div class="card-header text-center"> <div class="card-body"> <table class="table table-hover" cellpadding="3"> <thead class="bg-primary"> </thead> <tbody> <tr> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> </tr> <tr> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> </tr> <tr> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> <td> </td> </tr> </tbody> </table> </div> </div> </div> <!-- d-lg-block no oculta el compenente en tamaños grandes, d-none oculta en todos los demas tamaños <div class="col-md-4 d-md-block d-lg-block d-none">--> <div class="col-md-4 col-sm-12"> <div class="card"> <div class="card-header text-center conversor"> Conversor de divisas </div> <div class="card-body bg-primary"> <form> <div class="form-group"> <input type="number" class="form-control form-control-sm" id="txtCantidad" aria-describedby="emailHelp"> </div> <div class="form-group"> <select class="form-control form-control-sm"> </select> </div> <div class="form-group"> <select class="form-control form-control-sm"> </select> </div> <div class="form-group"> <input type="password" class="form-control" readonly id="txtA"> </div> </form> </div> </div> </div> </section>
gracias