If I have a system of linear equations in three variables, **in triangular form**, how can I line them up nicely in LaTex?

This is what I tried doing in a recent post. I used white dots as placeholders. Does anyone know of a more elegant way?

$\displaystyle \begin{aligned}

x&\; +& 4y&\; -& 2z&\; = 1 \\

{\color{white}.}&\; {\color{white}.}& y&\; -& 0.55z&\; = 0.35 \\

{\color{white}.}&\; {\color{white}.}& {\color{white}.}&\; {\color{white}.}& z&\; = 3

\end{aligned}$

And this is the code I typed (I took out the [tex] tags below):

Code:

\begin{aligned}
x&\; +& 4y&\; -& 2z&\; = 1 \\
{\color{white}.}&\; {\color{white}.}& y&\; -& 0.55z&\; = 0.35 \\
{\color{white}.}&\; {\color{white}.}& {\color{white}.}&\; {\color{white}.}& z&\; = 3
\end{aligned}

TIA.

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