It's called an Icosahedron
http://mathworld.wolfram.com/Icosahedron.html
A 20-sided solid shape is called a dodecahedron. It is one of the five Platonic solids and is characterized by having 12 regular pentagonal faces. Each vertex of a dodecahedron is where three faces meet. This shape is often used in games and modeling due to its symmetrical properties.
A polyhedron with 20 faces is called an icosahedron.
Depends. What shape is it?
the net of a shape is how many sides of a shapeThe net of a solid shape is a flat arrangement of its faces faces which can be folded together to make the solid shape. See related links, below.
A pentagonal prism.
Since a cube has 6 faces, you would be looking for a solid shape with only 2 faces and no such solid exists.
A 20-sided solid shape is called a dodecahedron. It is one of the five Platonic solids and is characterized by having 12 regular pentagonal faces. Each vertex of a dodecahedron is where three faces meet. This shape is often used in games and modeling due to its symmetrical properties.
an isosehedron has 20 faces
There is no regular solid with 13 faces.
A polyhedron with 20 faces is called an icosahedron.
tetrahedron
Depends. What shape is it?
a sphere
A polyhedron (solid shape formed by plane faces) with four faces is called a tetrahedron.
Shape
the net of a shape is how many sides of a shapeThe net of a solid shape is a flat arrangement of its faces faces which can be folded together to make the solid shape. See related links, below.
A pentagonal prism.