Let’s go through this together :)
First, I plotted the points on a graph (attaches photo).
Now, I am going to count the number of units between each point to find the perimeter.
6 + 3 + (square root of (1 squared + 4 squared)) + (square root of (1 squared + 3 squared)) + (square root of (2 squared + 4 squared)) = 15.8556546...
Rounded to the nearest one tenth, the answer is 15.9 units.