From what I know about slopes, I'm pretty sure that's the path you have to take is the picture below.
For each box, you have to do is count the change in the y-value and the change in the x-value between the points. Once you know those values, you have to divide y by x.
For example, take a look at the first graph. If you count, the change in the y-value is 3 units. The change in the x-value is 5 units. So, since slope is y/x, the slope is 3/5, which would take us to graph to the left.
Don't be afraid to ask any questions! Hope this helped.
Edit: Oh, and for the graphs that have lines that are completely vertical, the slope is undefined. For the graphs with lines that are completely horizontal, the slope is 0.