Selected elements

.

<informaltable border="1">
  <tr>
    <th>Col 1</th>
    <th>Col 2</th>
  </tr>
  <tr>
    <td>A1</td>
    <td>A2</td>
  </tr>
  <tr>
    <td colspan="2">B</td>
  </tr>
</informaltable>

<table border="1">
  <tr>
    <th>Col 1</th>
    <th>Col 2</th>
  </tr>
  <tr>
    <td>A1</td>
    <td>A2</td>
  </tr>
  <tr>
    <td colspan="2">B</td>
  </tr>
</table>

<informalequation>
  <m:math display="block">
    <m:mrow>
      <m:mi>E</m:mi>
      <m:mo>=</m:mo>
      <m:mrow>
        <m:mi>m</m:mi>
        <m:msup>
          <m:mi>c</m:mi>
          <m:mi>2</m:mi>
        </m:msup>
      </m:mrow>
    </m:mrow>
  </m:math>
</informalequation>

<math display="block">
  <mrow>
    <m:mi>E</m:mi>
    <m:mo>=</m:mo>
    <m:mrow>
      <m:mi>m</m:mi>
      <m:msup>
        <m:mi>c</m:mi>
        <m:mi>2</m:mi>
      </m:msup>
    </m:mrow>
  </mrow>
</math>

<informalequation>
  <mathphrase>
  $ |x| = \left\{
   \begin{array}{rl}
    -x & \mbox{if $x&lt;0$} \\
     x & \mbox{otherwise}
   \end{array}\right.$
  </mathphrase>
</informalequation>

<span class="mathphrase">
  $ |x| = \left\{
   \begin{array}{rl}
    -x & \mbox{if $x&lt;0$} \\
     x & \mbox{otherwise}
   \end{array}\right.$
</span>