In the XML file that I attached in my previous post, look at the HTML code of the Part's text where you will see:
\(
\large{
\dfrac{{a}x^{{c}}}{{b}x^{{d}}} = \hspace{39px} x
}
\)
<div style="display:inline-block;
position:relative;
font-size:120%;
font-family:'Times New Roman';
left:-53px;
top:0px">
{_0}
</div>
<div style="display:inline-block;
position:relative;
font-size:80%;
font-family:'Times New Roman';
left:-38px;
top:-6px;">
{_1}
</div>
where
font-size:120%;makes a larger font and
font-size:80%;a smaller one. Note that you can adjust the percentage as needed.