The perimeter of an equilateral triangle is 15 x + 30 units. Which expression can be used to show the side length of one side of the equilateral triangle? 15 (x + 2): Each side length is x + 2 units. 30 (one-half x + 1): Each side length is One-half x + 1 units. 5 (3 x + 6): Each side length is 3 x + 10 units. 3 (5 x + 10): Each side length is 5 x + 10 units.