A regular align with some macro-involvement would obtain the desired result:



\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\newcommand{\alignmath}[2]{\makebox[0pt][#1]{$\displaystyle#2$}}
\newcommand{\lmath}[1]{\alignmath{l}{#1}}
\newcommand{\rmath}[1]{\alignmath{r}{#1}}
\newcommand{\cmath}[1]{\alignmath{c}{#1}}
\begin{document}

\begin{align}
  &amp; \text{this is my first equation:}  &amp; \cmath{z=x}   &amp; \\
  &amp; \text{this is my second equation:} &amp; \cmath{z=x+y} &amp; \\
  &amp; \text{this is my third equation:} &amp; \lmath{z=x+y}  &amp; \\
  &amp; \text{this is my fourth equation:} &amp; \rmath{z=x+y} &amp; \\
  &amp; \text{this is my last equation:} &amp; z &amp;= x+y
\end{align}
\end{document}


\cmath inserts a zero-width box that is centred. The advantage here is that you maintain the align-like vertical spacing.

I've added \lmath and \rmath for completeness, since \makebox allows for left- and right-aligned boxes. Also, the vertical rule indicates the horizontal alignment with respect to the default align - also supported in the above syntax.

Left align equation description
How quickly can the loss of lactose tolerance onset in an adult?

Such as being able to process lactose normally to having notice symptoms associated with the inability to process lactose.

I am not asking how long it takes to digest food, but rather how long it takes for lactose intolerance to become noticeable (hours, days, weeks, months, years).
