\documentclass[12pt,russian]{article}
\usepackage[dvips]{graphics,graphicx}
\usepackage{amsmath,rotate}
\usepackage{epsfig}
\usepackage[english,russian]{babel}
\begin{document}
\begin{equation}
 {d \Vec{y} \over {dt}}=\Vec{f}(t,\Vec{y}) \hspace{1cm}
\eqno(4)
\end{equation}
\end{document}
