\documentclass[12pt]{article}
\usepackage{titlesec}
 
 \usepackage{amsfonts,amsmath,amssymb,latexsym}
 
 \textwidth=7in \textheight=8.8in \topmargin -0.2in
 
\oddsidemargin=-0.2in \evensidemargin=-0.2in
\titleformat{\section}
{\fontsize{70}{100}\selectfont\bfseries}
{\thesection}{10mm}{}
 \begin{document}
\section{ Basic idea of the kernel w-homotopy perturbation method (k-w-HpM)}

\end{document}
