А) 3/7 : 7/9 = 3/7 * 9/7 =27/49
б) 4/15 : 16/25 = 4/15 * 25/16 =1/3 * 5/4 =5/12
в) 5/28 : 15/42 = 5/28 * 42/15 = 1/2 * 3/3 = 1/2
г) 9/52 : 6/13 = 9/52 * 13/6 = 3/4 * 1/2 = 3/8
д) 56 : 7/8 = 56 * 8/7 =8*8=64
е) 3 3/4 : 4 3/8 = 15/4 : 35/4 = 15/4 * 4/35 = 15/35=3/7