Well, you have two ways to do this:
1) you could graph the points, connect them to make a line, and then find the height and width from one point to the other. The slope would then be height/width.
2) The more mathematical way: pick two x values (name them x1 and x2) and their corresponding y values (y1 and y2). Calculate (y2-y1)/(x2-x1). That is your slope!
For your problem: pick any two x values of the four (it doesn't matter which). Let's go with the first two (0 and 3) find their corresponding y values (5 and 7) and plug them into the equation: (7-5)/(3-0) = 2/3
2/3 is your slope, so the answer is C!
I hope this helps!! Let me know if you have ANY questions. :)
