Let x represent one side of equilateral triangle.
Next, we know that the perimeter of the equilateral triangle= side+side+side,so
P=x+x+x with the P=15x^3+33x^5 feet
15x^3+33x^5=3x
Divided both side by 3
(15x^3+33x^5)/3=3x/3
x=5x^3+11x^5
x=x³(5+11x²) feet. As a result, the length of each side is x³(5+11x²) feet. Hope it help!