4/8*3/7
1/2*3/5
6/8*9/12
8/9*11/4
15/20*1/2

4/8 * 3/7 = 12/56 = 3/14
1/2 * 3/5 = 3/10
6/8 * 9/12 = (1*9)/(8*2) = 9/16
8/9 * 11/4 = (2*11)/(9*1) = 22/9 = 2 4/9
15/20 * 1/2 = 15/40 = 3/8