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.