(15/98 - 17/28) : 4 5/21 + (4/40 - 3/20) * 21 3/7 = - 1 5/28выражением:= (30/196 - 119/196) : (89/21) + (4/40 - 6/40) * (150/7) == (- 89/196) * (21/89) + (-2/40) * (150/7) == - 21/196 + (-1/20) * (150/7) == - 3/28 + (- 15/14) == - 3/28 + (- 30/28 ) == - (30+3)/28 = - 33/28 = - 1 5/28
по действиям:1) 15/98 - 17/28 = (15 * 2 - 17*7)/196 = (30-119)/196 = - 89/1962) 4/40 - 3/20 = (4 - 3*2)/40 = -2/40 = - 1/203) - 89/196 : 4 5/21 = (- 89/196 ) * (21/89 ) = - 21/196 = - 3/284) - 1/20 * 21 3/7 = (-1/20) * (150/7) =- 15/14 = - 1 1/145) - 3/28 + (- 1 1/14) = - 3/28 + (-1 2/28) = - 1 5/28