Answer:
2 Tetrahedrons combined create an Octahedron.
Step-by-step explanation:
Despite the lack of information.
The Plato Polyhedrons are Tetahedron, Cube (Hexaedron), Dodecahedron, Octahedron and Icosahedron. They are regular ones, made up by regular plane figures.
An Octahedron can be built by combining two pyramids. Each Tetrahedron is made up by 4 equilateral triangle.