The altitude of an equilateral triangle is 15. what is the length of each side?

An equilateral triangle is a triangle where all sides are of equal lengths. So, the angles are of equal values as well which is 60. We use the angle and the height of the triangle to determine the side length. We do as follows:

tan (60) = 15 / base/2
base = 10√3 = side length

The answer should be c.