Answer:

Explanation:
1) take two of several points (for example, A(-8;0) and B(-3;1)); all the points needed are shown in the attached picture;
2) calculate the difference between y-coordinates and x-coordinates (for example, for A&B points y-difference is 1, x-difference is 5);
3) divide difference between y-coordinates by the difference between x-coordinates (for example, for points A&B it is 1/5=0.2). The result is the required slope.