Answer:
10
Step-by-step explanation:
im assuming that its an equalateral triangle because it makes the problem easier.
if you use the midpoint of the base as the point of where to make the parallels lines and draw them, you can easily find 4 congruent triangles, the side length of one of these congruent triangles is 2.5, and summing up the perimeter of the quadrilateral, you get 10.
