Correct Answer: Option D
An equilateral triangle is the one having all sides equal in length.
Let each side of the triangle is y units in length.
So, the perimeter of triangle will be = y + y + y = 3y units
This means,
3y = 15x + 30
3y = 3 (5x + 10)
y = 5x + 10
This means, each side of the equilateral triangle is 5x + 10 units in length.