Решение:

а) 6/25 : 9/5 = 6/25 * 5/9 = (6*5)/(25*9) = (2*1)/(5*3) = 2/15

б) 6 2/3 : 1 1/8 = (6*3+2)/3 : (1*8+1)/8 = 20/3 : 9/8 = 20/3 * 8/9 = (20*8)/(3*9) = 160/27 = 5 25/27

в) 8/27 : 8/9 = 8/27 * 9/8 = (8*9)/(27*8) = (1*1)/(3*1) = 1/3

г) 57 : 19/24 = 57 * 24/19 = (57*24)/19 = (3*24)/1 = 72

д) 9 5/7 : 1 23/28 = (9*7+5)/7 : (1*28+23)/28 = 68/7 : 51/28 = 68/7 * 28/51 = (68*28)/(7*51) = (68*4)/(1*51) = 272/51 = 5 17/51

е) 36/47 : 18 = 36/47 * 1/18 = (36*1)/(47*18) = (2*1)/(47*1) = 2/47