Vertically align text with display style fraction bar in array environment

Question

I'm typesetting a subsection of exercises using array environment. However, the vertical centers of exercise numbers do not align with the display style fraction bars (see the following figure). Other methods not using array are welcome, but please take into account that the vertical space between different rows can be changed (e.g. \renewcommand{\arraystretch}{0.5} in my code). I would appreciate any help with this situation.

\documentclass[a5paper,12pt]{book}
\usepackage[top=1.5cm,bottom=2cm,includehead=true,inner=2cm,outer=1.8cm]{geometry}
\usepackage{amsmath,amsthm,amssymb}
\usepackage{array}


\begin{document}

\chapter{Chap}

\section{Sec}

text text text text text text text text text text text text text text text text text text text text text text text text text 

\subsection{Exercise}

\begin{equation*}
\renewcommand{\arraystretch}{0.5}
\begin{array}{r@{\enspace } >{$\displaystyle}m{4.4cm}<{$} r@{\enspace } >{$\displaystyle}m{4.4cm}<{$}}
1.  & {\frac{1}{2}}+{\frac{1}{5}}=       & 2.   & {\frac{3}{4}}+{\frac{5}{8}}=              \\
    &                                    &      &                                           \\
3.  & {\frac{7}{9}}+{\frac{16}{21}}=     & 4.   & {\frac{5}{6}}+{\frac{11}{14}}=            \\
    &                                    &      &                                           \\
5.  & {\frac{15}{22}}+{\frac{11}{26}}=   & 6.   & {\frac{103}{10}}+8{\frac{5}{16}}=         \\
\end{array}
\end{equation*}

\end{document}

Answer 1

Why not going for simplicity?

\documentclass[a4paper,12pt]{book}
\usepackage{amsmath}
\usepackage{array}

\begin{document}

\chapter{Chap}

\section{Sec}

Some text for the section.
Some text for the section.
Some text for the section.
Some text for the section.
Some text for the section.

\subsection{Exercises}

\begingroup
\renewcommand{\arraystretch}{2.5}
\setlength{\arraycolsep}{0.5em}
\begin{tabular}{
  @{}
  l
  >{$\displaystyle}l<{$}
  @{\hspace{4em}}
  r
  >{$\displaystyle}l<{$}
  @{}
}
1.  & {\frac{1}{2}}+{\frac{1}{5}}=       & 2.   & {\frac{3}{4}}+{\frac{5}{8}}=              \\
3.  & {\frac{7}{9}}+{\frac{16}{21}}=     & 4.   & {\frac{5}{6}}+{\frac{11}{14}}=            \\
5.  & {\frac{15}{22}}+{\frac{11}{26}}=   & 6.   & {\frac{103}{10}}+8{\frac{5}{16}}=         \\
\end{tabular}
\endgroup

\end{document}

Answer 2

Anyway, the exercise numbers are typed on the base line, whereas the fraction bars are on the math axis.

If you absolutely want to align them, here is a way, using a simpler code, based on the tasks package:

\documentclass[a5paper,12pt]{book}
\usepackage[top=1.5cm,bottom=2cm,includehead=true,inner=2cm,outer=1.8cm]{geometry}
\usepackage{amsmath,amsthm,amssymb}
\usepackage{tasks}

\begin{document}

\chapter{Chap}

\section{Sec}

text text text text text text text text text text text text text text text text text text text text text text text text text

\subsection{Exercise}

\begin{tasks}[label=\raisebox{0.5ex}{\arabic*.} ](2)
\task $\dfrac{1}{2}+\dfrac{1}{5}= $
\task $ \dfrac{3}{4}+\dfrac{5}{8}= $
\task $ \dfrac{7}{9} + \dfrac{16}{21} = $
\task $ \dfrac{5}{6} + \dfrac{11}{14} = $
\task $ \dfrac{15}{22} + \dfrac{11}{26}= $
\task $ \dfrac{103}{10}+8\,\dfrac{5}{16} = $
\end{tasks}

\end{document}