First, square the trapezoid. Using one leg as side B of a triangle, make a right triangle with the new line as side A. You now have a right triangle with the apex pointing up, and 2 sides of 42.5 (let's say inches). Pythagorean gives us 42.5 squared + 42.5 squared = the square of the base, or 3612.5, which has a square root of 60.1. This is the base. Bisect the apex with a line to the base. You now have 2 congruent triangles with bases of 30.05. This also just happens to be the height of the triangles, and the trapezoid. If you take the outer triangle and "flop" it onto the other end of the trapezoid, you end up with a rectangle, whose height is 30.05, and whose length is 150 - 30.05, or 119.95. Then, Length x width will give you the area. (You do that part).