А)4/15:2/5 б)5/6:30 в)20:2 1/2 г)2 1/4:3 д)15:12

а)4/15:2/5=4/15 *  5/2=20/30=2/3 б)5/6:30=5/6* 1/30=5180=1/36 в)20:2 1/2=20/1 : 5/2=20/1*2/5=40/5=8  г)2 1/4:3=9/4 : 3/1=9/4*1/3=9/12=3/4  д)15:12=15/1*1/12=15/12=5/4=1 1/4  

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