Bonjour,
4/6 = (2 x 2) / (2 x 3) = 2/3
16/14 = (2 x 8) / (2 x 7) = 8/7
12/9 = (3 x 4) / (3 x 3) = 4/3
30/15 = (15 x 2) / (15 x 1) = 2
7/21 = (7 x 1) / (7 x 3) = 1/3
50/30 = (10 x 5) / (10 x 3) = 5/3
28/42 = (14 x 2) / (14 x 3) = 2/3
84/30 = (6 x 14) / (6 x 5) = 14/5.