Steps to replicate the issue (include links if applicable):

• Set mode to MathML
• Eenter the formula \begin{array}{lcr} z & = & a \\ f(x,y,z) & = & x + y + z \end{array}

What happens?:

Rendered as

What should have happened instead?:

In SVG rendered as

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

Chrome on Windows.