Hi, Not having too many ideas, I did this: is there not a more elegant way ? Thank you. Fabrice \definemathmatrix [pmatrix][matrix:parentheses][simplecommand=MATRIX] \starttext \startmidaligned \startxtable[align={middle,lohi},frame=off,offset=0.8ex] \startxrow \startxcell \m{P\times M=P} \stopxcell \startxcell \math{\iff} \stopxcell \startxcell \m{\MATRIX{x,y}\times \MATRIX{0.22,0.78;0.53,0.47}=\MATRIX{x,y}} \stopxcell \stopxrow \startxrow \startxcell \stopxcell \startxcell \m{\iff} \stopxcell \startxcell[align=right] \math{\startmathcases \NC 0.22x+0.53y=x \NR \NC 0.78x+0.47y=y \NR \stopmathcases} \stopxcell \stopxrow \startxrow \startxcell \stopxcell \startxcell \m{\iff} \stopxcell \startxcell[align=right] \m{0.78x-0.53y=0} \stopxcell \stopxrow \startxrow \startxcell \stopxcell \startxcell \m{\iff} \stopxcell \startxcell[align=right] \m{78x-53y=0} \stopxcell \stopxrow \stopxtable \stopmidaligned \stoptext