[tex]\frac{2}{7}-(1- \frac{5}{7})*( \frac{13}{2}- \frac{3}{4})= \\ \frac{2}{7}-(\frac{7-5}{7})*(\frac{26-3}{4})= \\ \frac{2}{7}-\frac{2}{7}*\frac{23}{4}= \\ \frac{2}{7}-\frac{1}{7}*\frac{23}{2}= \\ \frac{2}{7}-\frac{23}{14}= \\ \frac{4-23}{14}=- \frac{19}{14} [/tex]
/robèrtinni
