%@Dif:2 Calcule le plus simplement possible. \[ \Eqalign{ \frac23\times300&\kern1cm&\frac47\times49&\kern1cm&\frac79\times18&\kern1cm&\frac38\times328\cr \cr \frac45\times150&\kern1cm&\frac13\times750&\kern1cm&\frac12\times790&\kern1cm&\frac9{10}\times540\cr } \]