[OS X TeX] Space around equal sign

[Cleo]

Hi guys,

When I need to write some math, say $x=y+n$, I usually use $x~=~y~+~n$ to avoid
it breaks between lines. However, sometimes it appears an unwanted space before
and after the equal sign. I have tried to solve this by using $x~\!=\!~y~+~n$
but not always it works.

Is there a way to avoid an expression to break and maintain a "constant" space
around the equal sign?

Thanks in advance.

Cleo