\documentclass{article}

\usepackage[latin2]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[magyar]{babel}

\begin{document}

$x(t)+\dot{x}(t)+\ddot{x}(t)$, \\ 
$\tilde{z}=\hat{z}$, \\
$\vec{a}+\vec{b}=\vec{c}$, \\
$\bar{\jmath}=\check{\imath}$

\end{document}