check the picture below.
now, we're assuming the trapezoid is an isosceles trapezoid, namely AD = BC, and therefore the triangles are twins.
incidentally, b is the height of the trapezoid and likewise is also the altitude or height of the concrete triangle.
so we can simply get the area o the trapezoid, notice the bottom base is a+185+a, and then get the area of the concrete triangle and subtract the triangle from the trapezoid, what's leftover is just the vegetation area.
so that's the area of the trapezoid, now let's get the area of the triangle.
since we know 36 yd² cost 12 bucks, then how much will it be for 39475.018 yd²?