I want to write the optimization problem.
My code is:
\begin{alignat}{3}
& \underset{\framebox(100,10){}}{\text{minimize}} & \quad & \framebox(100,10){}\\
& \text{subject to} & & \framebox(100,10){},\\
& & & \framebox(100,10){},\\
& & & \framebox(100,10){},\\
& & & \framebox(100,10){},\\
& & & \max_{i=1,\ldots,l+m+n} \framebox(100,10){},\\
& & & \min_{i \in \mathbb{R}} \framebox(100,10){}.
\end{alignat}
However, I want to make the problem like this:

- minimize and subject to is aligned at center.
- constraints are aligned at left (except for subscript)



\mathclap{\text{some text}}with the simpler\clap{some text}. – Bernard Jun 14 '17 at 12:36\textfor the first one and\makeboxfor the second (which also removes the slightly anoying\rule). I have updated. – StefanH Jun 14 '17 at 14:05\rule{15pt}{0pt}before the framebox. It is just a distnace of 15pt, which seems to be enough. – StefanH Jun 15 '17 at 11:33