In addition, we need the cardinality of a fuzzy set which is defined as the sum of the grades of membership of each element, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\begin{equation*}|S| = \sum\limits_{x \in S} {m(x).} \end{equation*}\end{document}
