(найдите значение выражения ( 5 3/5-1 1/3):(7 7/12-2 1/4)* 1,25 Решите уравнение 2 2/3х-1 5/7=31/21

№11) 5 3/5 - 1 1/3 = 28/5 - 4/3 = (28 * 3 - 4 * 5)/15 = (84 - 20)/15 = 64/15 = 4 4/15;2) 7 7/12 - 2 1/4 = 91/12 - 9/4 = (91 * 1 - 9 * 3)/12 = (91 - 27)/12 = 64/12 = 16/3 = 5 1/3;3) 4 4/15 : 5 1/3 = 64/15 : 16/3 = 64/15 * 3/16 = 4/5;4) 4/5 * 1,25 = 0,8 * 1,25 = 1.Ответ: 1.№28/3х - 12/7 = 31/21;8/3х = 31/21 + 12/7;8/3х = (31 * 1 + 12 * 3)/21;8/3х = (31 + 36)/21;8/3х = 67/21;х = 67/21 : 8/3;х = 67/21 * 3/8;х = 67/56;х = 1 11/56.Ответ: 1 11/56.