1) 3/8 * 4/5 : 9/10 = 3/8 * 4/5 * 10/9 = 1/2 * 1/1 * 2/3 = 1/3
2) 6/7 : 3/5 * 1 2/5 = 6/7 * 5/3 * 7/5 = 2/1 * 1/1 * 1/1 = 2
3) 2 2/11 * 1 3/8 : 3/4 = 24/11 * 11/8 * 4/3 = 3/1 * 1/1 * 4/3 = 4
4) 11/23 * 3 2/7 : 5 1/2 = 11/23 * 23/7 : 11/2 = 11/23 * 23/7 * 2/11 = 2/7
5) 3/5 * (2 2/3 : 3 1/5) = 3/5 * (8/3 : 16/5) = 3/5 * (8/3 * 5/16) = 3/5 * 5/6 = 1/2
6) 1 1/8 * (9 1/3 : 1 3/4) = 1 1/8 * (28/3 : 7/4) = 9/8 * (28/3 * 4/7) = 9/8 * 16/3 = 3/1 * 2/1 = 6