effectue les calcul suivant en détaillant les étape de calcul ex:z=2x[8+(3+3)]
                                                                                           =2x[8+5]
                                                                                           =2x13
                                                                                           =26
b=-4-[5x(-2)+2-2x(-4)]
c=+(-4)x[(3+(4))x(-2-(-3))]