Answer:
3(x+4) = 18.6 or 3x+12 = 18.6
Step-by-step explanation:
Equilateral - All sides equal
Triangle - 3 sides
Since the perimeter is 18.6, we would need to add the sums of the sides. Since all three sides are equivalent, all we would have to do is multiply by 3, and that would be equivalent to the perimeter.