  <tr id="#15">
      <td style="text-align:right;">15</td>
      <td style="text-align:center;">&#128522;</td>
      <td style="text-align:left;">$$c{\bold e}_x = a{\bold e}_\alpha - b\tilde{\bold e}_\alpha$$</td>
      <td style="text-align:left;"><section><eqn><span class="katex-display"><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>c</mi><msub><mrow><mi mathvariant="bold">e</mi></mrow><mi>x</mi></msub><mo>=</mo><mi>a</mi><msub><mrow><mi mathvariant="bold">e</mi></mrow><mi>α<