>y</td>
</table>
<table border>
  <tr>
    <td style="width: calc(50% + 1px)">x</td>
    <td style="width: 100px">y</td>
</table>
<table border>
  <tr>
    <td style="width: calc(50%)">x</td>
    <td style="width: 100px">y</td>
</table>
<table border>
  <tr>
    <td style="width: calc(2 * 10% + 0.5 * 500px)">x</td>
    <td style="width: 100px">y</td>
</table>
</body>
</html>
