Г) 3/49 + 5/7 + 4/49 = (3/49 + 4/49) + 5/7 = 7/49 + 5/7 = 7/49 + 35/49 = 42/49
г) 7/15 + (2/15 + 1/5) = 1/5 + (2/15 + 7/15) = 1/5 + 9/15 = 3/15 + 9/15 = 12/15
г) 3/8 + 5/12 + 1/24 = 3/8 + (5/12 + 1/24) = 3/8 + (10/24 + 1/24) = 3/8 + 11/24 = 9/24 + 11/24 = 20/24
д) 7/10 + 2/15 + 11/30 = 7/10 + (2/15 + 11/30) = 7/10 + (4/30 + 11/30) = 7/10 + 15/30 = 21/30 + 15/30 =36/30 = 1 6/30
д) 3/16 + (1/16 + 5/8) = 5/8 + (3/16 + 1/16) = 5/8 + 4/16 = 10/16 + 4/16 = 14=16
д) 1/4 + 3/8 + 5/16 = 1/4 + (3/8 + 5/16) = 1/4 + (6/16 + 5/16) = 1/4 + 11/16 = 4/16 + 11/16 = 15/16
е) 1/12 + 1/18 + 1/12 = (1/12 + 1/12) + 1/18 = 1/12 + 1/18 = 3/36 + 2/36 = 5/36
е) (1/13 + 1/14) + 12/13 = (1/13 + 12/13) + 1/14 = 13/13 + 1/14 = 1 + 1/14 = 1 1/14
е) 5/7 + 3/14 + 1/21 = ( 5/7 + 3/14) + 1/21 = (10/14 + 3/14) + 1/21 = 13/14 + 1/21 = 39/42 + 2/42 = 41/42
Вот держи =)