Question 887325
<ul>Facts we will use:<ul>
1) Equilateral triangles have all the same side lengths
2) Perimeter of a triangle = the sum of all 3 side lengths
                           = 3*one side length(from fact 1)
3) The length of a side of a triangle is equal to the distance between the two vertices connected by that side.
4) The distance between two points is {{{d=sqrt((x2-x1)^2+(y2-y1)^2)}}}<br>

So we need to find the distance between the two given vertices and then multiply that by 3 to find the Perimeter(from facts above).<br>

Perimeter = 3*{{{sqrt((x2-x1)^2+(y2-y1)^2)}}}
= 3*{{{sqrt((-8-3)^2+(-5-7)^2)}}}
= 3*{{{sqrt((-11)^2+(-12)^2)}}}
= 3*{{{sqrt(121+144)}}}
3*{{{sqrt(265)}}}