MWE
\documentclass[a4paper,12pt]{book}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{lmodern}
\usepackage[svgnames]{xcolor}
\usepackage{empheq}
\definecolor{formula}{RGB}{255,255,170}
\newcommand*\mybox[1]{%
\colorbox{formula}{\hspace{1em}#1\hspace{1em}}}
\newcommand{\denklem}[1]{\begin{empheq}[box=\mybox]{align}{#1}\end{empheq}}
\begin{document}
\denklem{\frac{V}{\left(\dfrac{20}{9}\right)}=\frac{140-V}{20}}
\end{document}
The space above the left and right denominator is not equal. How can we equalize?
Note: I found a solution as follows. Is that right? So is this always done?
\denklem{\frac{V}{\raisebox{-1.5ex}{$\left(\dfrac{20}{9}\right)$}}=\frac{140-V}{20}}