To go from the first column to the second column, we have to divide the elements of the first column by 2.
miles: 16/2 = 8
hours:

To go from the second column to the third column, we have to divide the elements of the second column by 2.
hours:

miles: 8/2 = 4
The ratio in the first column is 16 to 3/4
The ratio in the second column is 8 to 3/8
The ratio in the third column is 4 to 3/16