Formula in a variable that can be referenced later

Question

Is there a way to put a formula in a variable (as in like a programming language variable) so that it can be referred to and rendered later? I was able to do this in Mathematica, but I'm moving away from Mathematica because I don't want to pay for it. I want to change to something more openly available like LaTex for displaying math formulas.

Note: I'm using Jupyter Notebook, which happens to use MathJax for LaTex rendering.

Though I mentioned programming language variables, Mathematica, and Jupyter Notebook, I am asking about doing this purely in LaTex (MathJax in my case).

I didn't have a lot of time with Mathematica, but here's an example of something that could be done in Mathematica

some_function = a/b
x = some_function/c
Display[x];

The result would be something like this:

Answer 1

Given your example, I would come up with this for pure LaTeX:

\documentclass{standalone}

\newcommand{\somefunction}{\frac{a}{b}}
\newcommand{\x}{\frac{\somefunction}{c}}

\begin{document}
    $\x$
\end{document}

Depending on the use cases, one could also consider placing the $ inside of the \newcommand, but this would limit the nesting.

Having no Jupyter at hand, I can not test, if this works also there.