Скобки

% Пример 1

\documentclass{article}

\usepackage{amsmath, amsfonts, amssymb}

\begin{document}
    $$
        \left [
            \begin{array}{l}
                x \le 10 \\
                x \ge 10
            \end{array}
        \right.
    $$
\end{document}

% Пример 2

\documentclass{article}

\usepackage{amsmath, amsfonts, amssymb}

\begin{document}
    $$
        \left [
        \textbf{magic! }
            \begin{array}{l}
                x \le 10 \\
                x \ge 10
            \end{array}
        \right \}
    $$
\end{document}