<<< native [ EArray [ AlignCenter ] [ [ [ EGrouped [ EIdentifier "x" , ESymbol Bin "+" , EDelimited "(" ")" [ Right (EFraction NormalFrac (ENumber "2") (ENumber "3")) ] ] ] ] , [ [ EDelimited "" ")" [ Right (EIdentifier "x") , Right (ESymbol Bin "+") , Right (EOver False (ESymbol Open "(") (ESymbol Bin "-")) , Right (EFraction NormalFrac (ENumber "2") (ENumber "3")) ] ] ] ] ] >>> mml $$\begin{array}{c}\hfill x+\left(\frac{2}{3}\right)\hfill \\ \hfill x+\stackrel{-}{(}\frac{2}{3})\hfill \end{array}$$