<!DOCTYPE HTML>
<html>
<head>
<title>Percent widths on table cells</title>
<style type="text/css">

td > table {
  border-spacing: 3px 5px;
  padding: 2px 3px 4px 5px;
}

td {
  border: none;
  padding: 0;
}

span {
  display: inline-block;
  width: 50px;
  background: fuchsia;
  color: fuchsia;
}

</style>
</head>
<body>

<table border><tr><td>
<table><tr>
<td style="background: yellow;color:yellow" width="50%"><span>x</span></td>
<td style="background:aqua;color:aqua"><span>x</span>&#x200b;<span>x</span>&#x200b;<span>x</span></td>
</tr></table>
</td></tr></table>

</body>
</html>