well, TP = RA, the heck does that mean? well, besides making the trapezoid an isosceles one, it means that ∡T = ∡R and ∡P = ∡A.
Now, the sum of all interior angles in a polygon is 180(n - 2), n = sides, this one has four sides so it has a total sum of interior angles of 180(4 - 2) = 360°.
