а) 3/7 - (1/2 + 1/4) = 3/7 - (2/4 + 1/4) = 3/7 - 3/4 = (12 - 21)/28 = -9/28
б) -3/7 + (1/14 - 2/21) = -3/7 + (3/42 - 4/42) = -3/7 - 1/42 = (18 - 3)/42 = 15/42 = 5/14
в) -2/5 + (1/10 - 7/15) = -2/5 + (3/30 - 14/30) = -2/5 - 11/30 = (6 - 55)/30 = -49/30
г) (2/5 - 9/10) + 1/3 = (4/10 - 9/10) + 10/30 = -5/10 + 10/30 = -1/2 + 1/3 = (-15 + 20)/30 = 5/30 = 1/6
д) (3/14 - 11/28) - 1/2 = (6/28 - 11/28) - 14/28 = -5/28 - 14/28 = (-5 - 14)/28 = -19/28
е) (2/7 - 1/14) - 5/21 = (6/14 - 1/14) - 5/21 = 5/14 - 5/21 = (15 - 14)/42 = 1/42
а) 3/7 - (1/2 + 1/4) = 3/7 - (2/4 + 1/4) = 3/7 - 3/4 = (12 - 21)/28 = -9/28
б) -3/7 + (1/14 - 2/21) = -3/7 + (3/42 - 4/42) = -3/7 - 1/42 = (18 - 3)/42 = 15/42 = 5/14
в) -2/5 + (1/10 - 7/15) = -2/5 + (3/30 - 14/30) = -2/5 - 11/30 = (6 - 55)/30 = -49/30
г) (2/5 - 9/10) + 1/3 = (4/10 - 9/10) + 10/30 = -5/10 + 10/30 = -1/2 + 1/3 = (-15 + 20)/30 = 5/30 = 1/6
д) (3/14 - 11/28) - 1/2 = (6/28 - 11/28) - 14/28 = -5/28 - 14/28 = (-5 - 14)/28 = -19/28
е) (2/7 - 1/14) - 5/21 = (6/14 - 1/14) - 5/21 = 5/14 - 5/21 = (15 - 14)/42 = 1/42