Replicating a tabular environment with an enumerate environment

Question

I would like to replicate a display obtained from a tabular environment with an enumerate environment. Here is the code for the tabular environment.

\documentclass{amsart}
\usepackage{makecell}
\begin{document}
\noindent \textbf{1.) }Compute the following sums. Express each sum as a fraction for which the only common divisor of the numerator and denominator is 1. \
\noindent \hspace*{2em}
\setlength{\tabcolsep}{0.6in}
\setlength{\extrarowheight}{3ex}
\begin{tabular}{@{}r@{}lr@{}lr@{}l}
\textbf{i.) }   &   $\displaystyle{\frac{3}{2} + \frac{4}{3}}$
&
\textbf{ii.) }  &   $\displaystyle{1 + \frac{2}{5}}$
&
\textbf{iii.) } &   $\displaystyle{\frac{9}{15} + \frac{2}{5}}$ \[1.2\normalbaselineskip]
\textbf{iv.) }  &   $\displaystyle{\frac{6}{39} + \frac{20}{52}}$
&
\textbf{v.) }   &   $\displaystyle{\frac{6}{25} + \frac{36}{75}}$
&
\textbf{vi.) }  &   $\displaystyle{\frac{10}{11} + \frac{20}{33}}$
\end{tabular}
\end{document}

Here is the code using the enumerate environment.

\documentclass{amsart}
\usepackage{enumitem}
\begin{document}
\noindent \textbf{1.) }Compute the following sums. Express each sum as a fraction for which the only common divisor of the numerator and denominator is 1. \
\noindent \hspace{2em}
\begin{enumerate}[label=\upshape\bfseries\roman.), leftmargin=4em, before=\itshape]
\item $\displaystyle{\frac{3}{2} + \frac{4}{3}}$
\item $\displaystyle{1 + \frac{2}{5}}$
\item $\displaystyle{\frac{9}{15} + \frac{2}{5}}$
\item $\displaystyle{\frac{6}{39} + \frac{20}{52}}$
\item $\displaystyle{\frac{6}{25} + \frac{36}{75}}$
\item $\displaystyle{\frac{10}{11} + \frac{20}{33}}$
\end{enumerate}
\end{document}