fontsize in mathml fractions

Good Afternoon;

I am new to MathML and this is my first encounter with this list.

When I create rational expressions with MathML I do not want the 
fontsize to decrease.  It does not in any textbook so should not on my 
webpages.
I have stumbled across a means (using <mstyle displaystyle=true >) of 
creating simple fractions with the fontsize of both numerator and 
denominator the same as any other character in the document.

However, when I create complex rational expressions I have not found a 
means of maintaining the proper fontsize.

The easiest example I can give is this page -- filled with complex 
rational expressions.
http://www.drdelmath.com/examples/mathjax_examples_rational_expression_complex_simplifying.htm

Can anyone tell me how to fix the problem or point me to a good resource.

Del