Saving the Baiji

With less than twenty left in the world, the Baiji dolphin is one of the most endangered species on Earth.  But you have a solution.  You've invented a duplicating machine so you can put one dolphin in and get two out!  But right now you only have a prototype that can duplicate coins. But once you have enough money from the prototype, you can build the full size duplicator. Test it out below after you solve the trapezoid problem.

Good luck!

Length of the midsegment:

Solve this problem to test the duplicator machine!