How to make a division line a bit longer than normal?

Question

\documentclass[preview,border=12pt,12pt]{standalone}

\usepackage{mathtools}

\begin{document}
$
\displaystyle
\begin{aligned}
-\frac{3x}{10} &= 6 \\
-\frac{3}{10}x &= 6\\
        x       &= \frac{6}{-\tfrac{3}{10}}\\
                &= -\frac{\tfrac{6}{1}}{\tfrac{3}{10}}\\
                &= - \frac{6}{1}\times \frac{10}{3} \\
                &= -20
\end{aligned}
$
\end{document}

Result

Expected

Answer 1

I don't think it's useful: the fraction line on the formula axis (midway of the = sign) is sufficient to tell the reader what's the main one.

Using \; is perhaps exaggerated, try with \,.

\documentclass{article}
\usepackage{mathtools}

\newcommand{\Mfrac}[2]{% main fraction
  \frac{\;#1\;}{\;#2\;}%
}

\begin{document}

\[
\begin{aligned}
-\frac{3x}{10} &= 6 \\
-\frac{3}{10}x &= 6\\
             x &= \Mfrac{6}{-\tfrac{3}{10}}\\
               &= -\Mfrac{\tfrac{6}{1}}{\tfrac{3}{10}}\\
               &= - \Mfrac{6}{1}\times \Mfrac{10}{3} \\ % <-- is it good here?
               &= -20
\end{aligned}
\]
\end{document}

Answer 2

Perhaps you can manually add some white space by, say, ~, \, or even \hspace?

\[
    \begin{aligned}
        -\frac{3x}{10} &= 6 \\
        -\frac{3}{10}x &= 6\\
                x       &= \frac{6}{-\tfrac{3}{10}}\\
                        &= -\frac{~\tfrac{6}{1}~}{\tfrac{3}{10}}\\
                        &= - \frac{~6~}{1}\times \frac{10}{3} \\
                        &= -20
    \end{aligned}
\]