Question 862605
Let s equal one side of the triangle
equilateral triangle P = Pentagon with s-3 sides perimeter
{{{3s=5(s-3)}}}
Distribute the 5
{{{3s=5s-15}}}
Subtract 5s from both sides
{{{-2s=-15}}}
Divide both sides by -2
{{{s=7.5}}}
Each side is 7.5, so the perimeter is 3(7.5), or <h3>22.5</h3>