There are two ways to include mathematical formulae as inlines within a paragraph.
If your expressions are relatively simple, you can enclose them inside an element like this:
This will show all letters in italics. Here is an example:
We must prove that a2<bx for all cases.
Here is the source for that example:
We must prove that <phrase role='math' >a<superscript >2</superscript ><b<subscript >x</subscript ></phrase > for all cases.