\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}

\thispagestyle{empty}
\begin{document}
\[
\alpha = \dfrac{360 \cdot 2}{7} - 90 = \dfrac{90}{7} = 12 + \dfrac{6}{7}
\]
\end{document}
