\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{ifluatex}
\usepackage{microtype}
\DeclareMathOperator{\TL}{TL}
\DeclareMathOperator{\TR}{TR}
\begin{document}
\[\TL(L, K_1, K_2) = (L - K_1)^+ - (L - K_2)^+\]
\[\TR(R, K_1, K_2) = (R - 1 + K2)^+ - (R - 1 + K_1)^+\]
\[S(L, R, K_1, K_2) = \frac{K_2 - K_1 - \TL(L, K_1, K_2)- \TR(L, K_1, K_2)}{K_2-K_1}\]
\[L = L_0 + \tilde{L}\]

\end{document}