Example

Here is some presentation MathML -- $x+3+y$ -- and here is some more -- ${\sqrt{a+b}}^{27}$

Here is some content MathML -- $f(x)$ -- and some more -- $\sqrt{x+y+z}$

And here is some hairy content MathML: $\sqrt{\sqrt{{\displaystyle \frac{\alpha +\beta }{a+xyz+d^{{\displaystyle \frac{3}{2}}}}}}+{\displaystyle \frac{1}{e^x+\sqrt{x^2-y^2}}}}$