Var

The HTML   element, or variable, represents a variable in a mathematical expression or a programming context. The rendered content is italicized, much like the  element. This element should only be used if the content indicates a variable name. Do not use this element if the aim is solely to italicize text. Use CSS or the  element for this purpose.

Attributes
See Global HTML Attributes.
 * Global Attributes

HTML example:

5 x + 5 = 20

That produces: 5x + 5 = 20

On Wikia, it is possible to use the wiki markup  element to render math content.

$$5x+5=20$$

produces: $$5x+5=20$$