JSFiddle - React, Tailwind, and code Playground

HTML

<form method="post" name="formoferta" action="envia1.php">
<table border="1" cellpadding="0" cellspacing="0" bordercolor="#000000" id="formoferta2">
    <tr>
        <th>Und</th>
            <th>Descrição</th>
            <th>Imagem<br>Produto</th>
            <th>Classificação<br>Fiscal</th>
            <th>Qtde</th>
            <th>Vlr. Unitario</th>
            <th>Vlr. Subtotal</th>
            <th colspan="2">Prazo de<br>Entrega</th>
        </tr>
  <tbody>
        <tr class="linhas">
            <td><input type="text" name="und[]" id="und" style="text-align:center" /></td>
            <td><textarea name="desc[]" id="desc" cols="25" rows="5"> </textarea></td>
            <td><textarea name="img[]" id="img" cols="20" rows="5"> </textarea></td>
            <td><input type="text" name="clfiscal[]" id="clfiscal"  style="text-align:center" /></td>
            <td class="class_unit"><input type="text" name="qtde[]" id="qtde"  style="text-align:center" /></td>
            <td class="class_quant"><input type="text" name="vlrunt[]" id="vlrunt" style="text-align:center" /></td>
            <td class="class_total"><input type="text" name="vlrsub[]" id="vlrsub" style="text-align:center" /></td>
            <td><input type="text" name="prazo[]" id="prazo" style="text-align:center" /></td>
            <td><a href="#" class="removerCampo" title="Remover linha"><img src="http://www.ceaderlagos.com.br/admin/imagens/excluir.gif" border="0" id="excluir" /></a></td>
  </tr>        
        <tbody>
  <tr>
<td colspan="9">
    <strong>TOTAL:</strong></td>
  </tr>
        <tr>
<td colspan="9">
    <a href="#" class="adicionarCampo" title="Adicionar item"><img src="http://www.neip.info/html/imagens/site/ic-inserir.gif" border="0" / id="inserir"></a></td>
  </tr>
        <tr>
  <td align="right" colspan="9"><input type="submit" id="btn-cadastrar" value="ENVIAR OFERTA" /></td>
  </tr>  
</table>
</form>

JavaScript

function removeCampo() {
$(".removerCampo").unbind("click");
$(".removerCampo").bind("click", function () {
  if($("tr.linhas").length > 1){
$(this).parent().parent().remove();
  }
});
  } 
  $(".adicionarCampo").click(function () {
novoCampo = $("tr.linhas:first").clone();
novoCampo.find("input").val("");
novoCampo.insertAfter("tr.linhas:last");
removeCampo();
  });
/*
  $("vlrunt").keyup(function(){
    var qtde  = $("#qtde").val();
    var vlrunt= $("#vlrunt").val();
    $("#vlrsub").val(parseFloat(vlrunt) * parseFloat(qtde));
  });
*/
$(document).on('keyup', 'input[name="vlrunt[]"]', function(){
    var tr = $(this).closest('tr');
    var qtde  = tr.find('input[name="qtde[]"]').val();
    var vlrunt = $(this).val();
    if (qtde && vlrunt){
        tr.find('input[name="vlrsub[]"]').val(parseFloat(vlrunt) * parseFloat(qtde));
    }
});