We can start to answer this question taking into account that the rate of change is given by:

Then, we have from the table that we have three different values for y and three different values for x.
First, let us check that this rate of change is the same, that is if it is linear (it can be represented by a line) for these three different points:
x1 = 30
y1 = 1.5
x2 = 60
y2 = 3
Then, we have:

We have that the rate of change is 0.05 miles per minute.
Let us check the second rate of change:
x1 = 60
y1 = 3
x2 = 90
y2 = 4.5
Then, we have that the rate of change is:

We got the same rate of change of 0.05 miles per minute in both cases. Therefore, the rate of change in distance with respect to time is 0.05 miles per minute.