Answer :

AL2006
The perimeter is the sum of the lengths of the three sides.

To find the perimeter, you need to find the lengths of the three sides.

For each side, you are given the points at the two ends.You need to find the distance between those two points.

Once you have all thee distances, add them up.

That's how.
MathG33k
Well I'm not just going to tell you the answer, you need to "experience" how you do it. Basically you use the distance formula, which I'll show you in a bit, to fine the length of the segments. Then you just add them up.
[tex] \sqrt{ (x_{2}- x_{1}) ^{2} +(y_{2}-y_{1})^{2}[/tex]