2/5 = 4/10 = 6/15 = 8/20 = 10/25 = 12/30 = 14/35
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a) 12/18 = 2/3 ; 24/44 = 6/11 ; 8/12 = 2/3
б) 12/32 = 3/8 ; 10/15 = 2/5 ; 15/12 = 5/4
в) 12/16 = 3/4 ; 10/45 = 2/9 ; 25/40 = 5/8
г) 6/36 = 1/6 ; 20/36 = 5/9 ; 6/18 = 1/3