The area of the 3 trapezoid would be all equal because the formula of the area of the trapezoid is : A = h (b1 + b2) / 2 since the length of the base are equal in all three trapezoid, then the angle is not part in the equation of the area so the angle of the trapezoid does not affect its area. so that is why all the three trapezoid have equal area even with different angles.
The height is 26 miles. Multiply that by 2 which gets 52 and then subtract that from 84. That gives you 32 which means the sum of the lengths is 32/2 which is 16 miles