Сократим каждую дробь:
8/12 = (2*4)/(3*4) = 2/3
12/16 = (3*4)/(4*4) = 3/4
12/18 = (2*6)/(3*6) = 2/3
24/40 = (3*8)/(5*8) = 3/5
18/27 = (2*9)/(3*9) = 2/3
20/70 = (2*10)/(7*10) = 2/7
8/36 = (2*4)/(9*4) = 2/9
30/75 = (2*15)/(5*15) = 2/5
Ответ: 2/3, 3/4, 2/3, 3/5, 2/3, 2/7, 2/9, 2/5