Вычислите: а)(5!+6!+7!):(8!-7!) б)(18!-17*17!-16*16!):(17!-16!)

а)  5!*(1+6+6*7)            5!* 49                          49                     1       ___________  =  ____________   =  _________  = _____  =  1/6         7!*(8-1)                    5!*6*7*7                    6*49                  6       б)  16!* ( 17*18-17*17-16)           16!* (17*(18-17)-16)         16!* (17*1-16)        16!*1         1      ___________________   =  _________________ =  ____________  =  _____ = ____ = 1/16            16!* (17-1)                               16!* 16                               16!*16                    16!*16      16