Well, if we were to calculate slope from a graph, then we would look at the rise/Run but since we have to calculate it from a table of values, we will look at the first differences. In rise/Run, the rise is the Y while the X is the run so, on that basis, we can calculate the slope it rate of change from this table of values.
1. Rise = Y
We can see that each time that we are going to the next term, we are subtracting by and going down by 1 so, our rise is -1 while when we look at our run, each time, we are adding 3 units to get to the next term, so our Rise/Run would by -1/3.
So, in conclusion, the slope from the given table is: -1/3.