Hyphen Use in Mathematical Texts

I am proofing a range of workbooks for senior high school Mathematics. One of the areas I'm looking to be consistent is the use of hyphens in certain instances.

In reference to a 90 degree triangle, should it always be hyphenated to "right-angled", or "right angled"?

Similarly in reference to labelling of axes on the Cartesian plane, "x-axis" or simply "x axis"?

Lastly, when it comes to referencing variable values: "In the graph y = ax + c the a value" or should it be "a-value"? I use italics when it comes to using variables so they don't look like random typos, but still wonder about the hyphenation in this case.

I know these are small things, but I like to be accurate and consistent, especially when it comes to educational media as children (especially in the third world) have a hard enough time figuring out the content without still having to wade through inconsistent and inaccurate typing conventions.

Thanks.