A star
Rohmbus is a four sided figure (quadrilateral) that is made up of two equilateral triangles
Yes. You can always draw a "diagonal" line between opposite corners of any four-sided figure. Then, cutting along that line, you wind up with two triangles out of which the figure could have been made.
A rectangular prism
Yes, an octagon could be considered to be made out of 8 triangles.
A star
Tetrahedron.
Rohmbus is a four sided figure (quadrilateral) that is made up of two equilateral triangles
Such at figure - as described - could not be made as a solid geometric shape.
Yes. You can always draw a "diagonal" line between opposite corners of any four-sided figure. Then, cutting along that line, you wind up with two triangles out of which the figure could have been made.
A rectangular prism
A composite figure is a figure that is made up of several smaller geometric figures like triangles, circles, or rectangles.
Yes, an octagon could be considered to be made out of 8 triangles.
Yes
a star
A regular tetrahedron
A pyramid could be constructed from 4 or more triangles.