For the first part remember that an equilateral triangle is a triangle in which all three sides are equal & all three internal angles are each 60°. <span>So x-coordinate of R is in the middle of ST = (1/2)(2h-0) = h And for the second </span><span> since this is an equilateral triangle the x coordinate of point R is equal to the coordinate of the midpoint of ST, which you figured out in the previous answer. Hope this works for you</span>