First of all, you need to understand what you mean by "the ratio of a table."
The ratio of any y-vlaue to any corresponding x-value is not a constant here, so that is apparently not what you're talking about.
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When you plot the points on a graph, they are all on a straight line. That line has a slope of -1, which you can figure from the graph or from the table. Perhaps this is what you're asking.
Pick two (different) pairs of x- and y-values, for example, (x, y) = (40, 0) and (20, 20). Now, compute the difference in y-values and divide that by the difference in corresponding x-values.
... y-difference = (20 - 0) = 20
... x-difference = (20 - 40) = -20
Then the ratio of these is
... (y-difference)/(x-difference) = 20/-20 = -1
