I used table as below to do fraction addition:
<table border="0">
<tbody>
<tr>
<td>
<div style="border-bottom-width: 2px; border-bottom-style: solid; border-bottom-color: black; padding-bottom: 4px; font-size: medium; font-family: verdana;">1</div>
<div style="padding-top: 4px; font-size: medium; font-family: verdana;">2</div>
</td>
<td><span style="font-size: medium; font-family: verdana;">+</span></td>
<td>
<div style="border-bottom-width: 2px; border-bottom-style: solid; border-bottom-color: black; padding-bottom: 4px; font-size: medium; font-family: verdana;">1</div>
<div style="padding-top: 4px; font-size: medium; font-family: verdana;">3</div>
</td>
<td><span style="font-size: medium; font-family: verdana;">=</span></td>
<td>
<div style="border-bottom-width: 2px; border-bottom-style: solid; border-bottom-color: black; padding-bottom: 4px; font-size: small; font-family: verdana;">{1:SHORTANSWER:%100%5#
~*#
}</div>
<div style="padding-top: 4px; font-size: small; font-family: verdana;">{1:SHORTANSWER:%100%6#
~*#
}</div>
</td>
</tr>
</tbody>
</table>
Did I make things overly complex?