Put one piece into the tortoise and fit remaining to fill tray.
The objective of 6 out of 7 is to put one of the seven pieces (all tetrahexes) into the tortoise and use the remaining 6 to fill the upper tray completely. Based on the question raised by James Kerley. 4 other symmetrical shapes with the same rule available + 5 shapes that have only one solution with just one subset of 6 pieces. Design: © Alexander Magyarics