а) 4/15:2/5 = 4/15*5/2 = 20/30=2/3
б) 5/6:30 = 5/6: 30/1 = 5/6*1/30 = 5/180 = 1/36
в) 20:2 1/2 = 20/2,5 = 8 или 20/1 : 5/2 = 20/1*2/5 = 40/5 = 8
г) 2 1/4: 3 = 2,25/3 = 0,75 или 9/4:3/1 = 9/4*1/3 = 9/12 = 3/4
д) 15: 12 = 1,25 или 15/1 : 12/1 = 15/1*1/12 = 15/12 = 1 3/12 = 1 1/4