如何在表格下方制作不同宽度的表格行？

<table>
  <tr>
    <th>Header 1</th>
    <th>Header 2</th>
    <th>Header 3</th>
  </tr>
  <tr>
    <td>Content 1</td>
    <td>Content 2</td>
    <td>Content 3</td>
  </tr>
  <tr>
    <td colspan="2">Wide Content 1</td>
    <td>Narrow Content 2</td>
  </tr>
</table>

table {
  width: 100%;
}

th, td {
  border: 1px solid black;
  padding: 8px;
}

td[colspan="2"] {
  width: 70%;
}

td {
  width: 15%;
}