8-4,2:(2_5/14 - 1_4/21)= 4,4
3 2 1
1) 2_5/14 - 1_4/21 = 2_15/42 - 1_8/42 = 1_7/42
2) 4,2 : 1_7/42 = 42/10 : 49/42 =42/10 * 42/49 = (42*42) / (10*49) =
= (6 * 6) / 10=36/10 = 3,6
3) 8-3,6 = 4,4
8-4,2:(2_5/14 - 1_4/21)= 4,4
3 2 1
1) 2_5/14 - 1_4/21 = 2_15/42 - 1_8/42 = 1_7/42
2) 4,2 : 1_7/42 = 42/10 : 49/42 =42/10 * 42/49 = (42*42) / (10*49) =
= (6 * 6) / 10=36/10 = 3,6
3) 8-3,6 = 4,4
ответ: 4.4