Re: [MiKTeX] line in equation

[Philip G. R. <phi...@un...>]

> I'm sure you will get a better answer, ...

Yep, sorry, but here's one (the spaces are just for readability):

\begin{array}{lclcr}
  ax & + & by & = & 20 \\
  ax & - & by & = & 10 \\
  \hline
     &   & ax & = & 10
\end{array}

Note that the use of l, c and r above is deigned to get the best alignment,
but
you may want to change them.

N.B. The array environment MUST be used inside a math environment (e.g.,
$...$
or \begin{equation} ... \end{equation})

Cheers,  Phil