# Spacing problem with \phantom in array

Using

$\begin{array}{ccc} x & := & \phantom{ a + } b + c\\ y & := & a \phantom{ + b } + c\\ z & := & a + b \phantom{ + c } \end{array}$

I get

which is not quite what I hoped for as my "phantoms" don't take as much space as expected.

How can I correct this?

Thanks!

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