Answer:
-1
Step-by-step explanation:
Since two points are given, we can determine the slope with these. (1,2) and (2,1) are a negative slope, because one value is increasing, and the other value is decreasing, whichever way you go. When you connect the points, the rise over run is -1 over 1, which is -1/1, or simply -1. The slope is -1.