Ответ:

а) 4/15 : 11/75 = 4/15 * 75/11 = 20/11;

б) 9/25 : 2 3/5 = 9/25 : (2 * 5 + 3)/5 = 9/25 * 5/13 = 9/65;

в) 1 4/9 : 1 1/5 = (9 + 4)/9 : (5 + 1)/5 = 13/9 * 5/6 = 65/54;

г) 4/5 : 4 : 1 4/5= 4/5 * 1/4 * 5/9 = 20/180 = 1/9;

д) 3/5 : 1/4 : 7/12 = 3/5 * 4 * 12/7 = 144/35;

е) 2/5 : 3/4 : 5/12 = 2/5 * 4/3 * 12/5 = 1/5 * 2 * 4/5 = 8/25;

ж) 6 : 1 4/8 : 8/12 = 6 * 8/12 * 12/8 = 6;

з) 2 1/3 : 3 2/3 : 4/9 = 7/3 * 3/11 * 9/4 = 63/44;

и) 14/15 : 2 2/6 : 12 = 14/15 * 6/14 * 1/12 = 1/15 * 1/2 = 1/30.