The base of the building is an equilateral triangle 180 meters on each side. the height of the prism is 25m. find the height, of the triangular base.

What is your end goal?  I'd bet you're supposed to calculate the volume fo the building.

If the base is in the form of an equilateral triangle 180 m on each side, then the perpendicular distance from any vertex of the triangle to the opposite side is found using the formula h = (180 m) sin (60 deg), or 180sqrt(3)/2, or 90sqrt(3).

The area of the base is A = bh/2, which here is A = [(180 m)(90sqrt(3))], or
28059 square meters.  Then the VOLUME is (28059 m^2)(25 m) = 701475 cubic meters.