We find the perimeter as follows:
[tex]p=\sqrt[]{(18-13)^2+(8-8)^2}+\sqrt[]{(3-18)^2+(13-8)^2}+\sqrt[]{(15-3)^2+(13-13)^2}+\sqrt[]{(13-15)^2+(8-13)^2}[/tex]That is equal to:
[tex]p=38.19655311[/tex]We have that the perimeter of the parallelogram is approximately 38.2 units.
We determined it by finding the distance between the points and adding them.