а) 8*11/33*4 = 2*1/3*1 = 2/3
б) 18*25/75*12 = 3*1/3*2 = 3/6 = 1/2
в) 18*25/15*12 = 3*5/3*2 = 15/6 = 2 3/6 = 2 1/2
г) (6*7+7+5)/49 = 6/7 + 1/7 + 5/49 = 7/7 + 5/49 = 1 5/49
№ 61
а) 4/5 + 3/7 = 28/35 + 15/35 = 43/35 = 1 8/35
б) 5/12 + 9/20 = 25/60 + 27/60 = 52/60 = 13/15
в) 5/18 + 4/45 = 25/90 + 8/90 = 33/90 = 11/30
г) 12/17 + 27/34 = 24/34 + 27/34 = 51/34 = 1 17/34 = 1 1/2
№ 68
а) 5/16 + 11/12 = 15/48 + 44/48 = 59/48 = 1 11/48
б) 7/24 - 5/18 = 21/72 - 20/72 = 1/72
в) 4/35 + 1/28 = 16/140 + 5/140 = 21/140
г) 11/63 - 5/43 = 473/2709 - 315/2709 = 158/2709