There are two ways that you can do this.
First Method
Slope Formula:

7 is y2, 5 is y1, 2 is x2, and 3 is x1.

Therefore, the slope is -2. (aka "m = -2")
Second Method
Get a graph. Mark the two points on the graph and draw a line. After that, do the rise over run method. Go several units up and several units over. If the slope is going up to the left, then there is a negative slope. If the line is going up to the right, then there is a positive slope. (pictures of the graph down below)
I hope this helps! Let me know if I got something wrong.
(also check my profile and click on the question i asked. i can help you with more on there :D )