\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath,amsfonts}
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\begin{document}
\begin{equation*}
    \aligned 
      x[k+1] &= f(x[k], u[k]), \quad && x[k]\in{\Bbb R}^n,\, u\in{\Bbb R}, \\
      y[k] &= h(x[k], u[k]), && y\in{\Bbb R},
    \endaligned
\end{equation*}
\end{document}