The rate of change is measured by the slope m.
In case of y=3x-6, the slope is the coefficient of x, that is, the slope m is

Now, in the case of the table, we must find the slope m by choosing two points. The slope formula in this case is

where we chose:

Then, by substituting these values into the slope formula, we have

By comparing the slopes, we can see that the function represented in the table has the greatest rate of chance because 3.5>3