Answer:
30 ft
Explanation:
The perimeter of the square is 4 times the side length:
4 × 45 ft = 180 ft
If that is twice the length of the perimeter of the triangle, then the triangle's perimeter is (180 ft)/2 = 90 ft
The perimeter of an equilateral triangle is 3 times the side length, so each side of the triangle is ...
(90 ft)/3 = 30 ft . . . triangle side length