Задание номер 3, срочно!
-9/20 + 7/40 = (-18+7)/40 = -11/40 13/24 - 5/6 = 13/24 - 20/24 = (13-20)/24= 7/24 -2/7-16/21= -6/21-16/21 = (6+16)/21 =22/21 = 1 целая 1/21