You Do The Maths

Having built a cryptex I discovered maths toys. The question arose, what if you could combine the two. The result is a cryptex that only opens when a mathematical identity is made. The cryptex has an X ring of numbers, a function ring of operators, a Y ring, an equals ring and a Z ring. To open you need to get the rings to make a simple arithmetic expression. The numbers on the X, Y and Z rings have been deliberately chosen so that the user can deduce the answer in a small number of steps.

All the pieces are capable of being printed without support.