1) 6/11*4/7. 2) 7/20*10/21. 3) 8/9*27/32. 4) 23/28*49/46. 5) 34/86*43/51. 6) 7/18*90/77. 7) 63/64*48/91. 8) 36/85*34/39

6/11 * 4/7 = (6*4) / (11*7) = 24/77

7/20 * 10/21 = (7*10) / (20*21) = (1*1) / (2*3) = 1/6

8/9 * 27/32 = (8*27) / (9*32) = (1*3) / (1*4) = 3/4

23/28 * 49/46 = (23 * 49) / (28*46) = (1*7) / (4*2) = 7/8

34/86 * 43/51 = (34*43) / (86*51) = (34*1) / (2*51) = 17/51 = 1/3

7/18 * 90/77 = (7*90) / (18*77) = (1*10) / (2*11) = 5/11

63/64 * 48/91 = (63*48) / (64*91) = (7*9*6*8) / (8*8*7*13) =

= (9*3) / (4*13) = 27/52

36/85 * 34/39 = (36 * 34) / (85*39) = (3*12 * 2*17) / (5*17*3*13) =

= (12*2) / (5*13) = 24/65