To find the distance between 2 points, we start off by subtracting 2 x values. For the first 2 points, we do (3-(-1))=4. Next, we square it - 4^2=16. We then repeat with the y values - 7-(-5)=12 and 12^2=144. We then add the squares to get 16+144=159, and get the square root of that (sqrt(159)). Repeat the process for the other points until you have the distance from the second point to the third point and the third point to the first point, and then add them all up!
